| Message ID | 1373409659-22383-1-git-send-email-msw@amazon.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: > From: Xi Xiong <xixiong@amazon.com> > > [ note: I've just cherry picked this onto net-next, and only compile > tested. This a RFC only. -msw ] > Should probably rebase it on net.git because it is a bug fix. Let's worry about that later... > Currently the number of RX slots required to transmit a SKB to > xen-netfront can be miscalculated when an interface uses a MTU larger > than PAGE_SIZE. If the slot calculation is wrong, xen-netback can > pause the queue indefinitely or reuse slots. The former manifests as a > loss of connectivity to the guest (which can be restored by lowering > the MTU set on the interface). The latter manifests with "Bad grant > reference" messages from Xen such as: > > (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 > > and kernel messages within the guest such as: > > [ 180.419567] net eth0: Invalid extra type: 112 > [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 > [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 > > BUG_ON() assertions can also be hit if RX slots are exhausted while > handling a SKB. > > This patch changes xen_netbk_rx_action() to count the number of RX > slots actually consumed by netbk_gop_skb() instead of using nr_frags + 1. > This prevents under-counting the number of RX slots consumed when a > SKB has a large linear buffer. > > Additionally, we now store the estimated number of RX slots required > to handle a SKB in the cb overlay. This value is used to determine if > the next SKB in the queue can be processed. > > Finally, the logic in start_new_rx_buffer() can cause RX slots to be > wasted when setting up copy grant table operations for SKBs with large > linear buffers. For example, a SKB with skb_headlen() equal to 8157 > bytes that starts 64 bytes 64 bytes from the start of the page will Duplicated "64 bytes". And this change looks like an improvement not a bug fix. Probably submit a separate patch for this? > consume three RX slots instead of two. This patch changes the "head" > parameter to netbk_gop_frag_copy() to act as a flag. When set, > start_new_rx_buffer() will always place as much data as possible into > each RX slot. > > Signed-off-by: Xi Xiong <xixiong@amazon.com> > Reviewed-by: Matt Wilson <msw@amazon.com> > [ msw: minor code cleanups, rewrote commit message, adjusted code > to count RX slots instead of meta structures ] > Signed-off-by: Matt Wilson <msw@amazon.com> > Cc: Annie Li <annie.li@oracle.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Cc: Ian Campbell <Ian.Campbell@citrix.com> > Cc: netdev@vger.kernel.org > Cc: xen-devel@lists.xenproject.org > --- > drivers/net/xen-netback/netback.c | 51 ++++++++++++++++++++++-------------- > 1 files changed, 31 insertions(+), 20 deletions(-) > > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > index 64828de..82dd207 100644 > --- a/drivers/net/xen-netback/netback.c > +++ b/drivers/net/xen-netback/netback.c > @@ -110,6 +110,11 @@ union page_ext { > void *mapping; > }; > > +struct skb_cb_overlay { > + int meta_slots_used; > + int peek_slots_count; > +}; > + > struct xen_netbk { > wait_queue_head_t wq; > struct task_struct *task; > @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > { > unsigned int count; > int i, copy_off; > + struct skb_cb_overlay *sco; > > count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); > > @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > offset = 0; > } > } > + > + sco = (struct skb_cb_overlay *) skb->cb; > + sco->peek_slots_count = count; > return count; > } > > @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, > } > > /* > - * Set up the grant operations for this fragment. If it's a flipping > - * interface, we also set up the unmap request from here. > + * Set up the grant operations for this fragment. > */ > static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > struct netrx_pending_operations *npo, > struct page *page, unsigned long size, > - unsigned long offset, int *head) > + unsigned long offset, int head, int *first) > { > struct gnttab_copy *copy_gop; > struct netbk_rx_meta *meta; > @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > if (bytes > size) > bytes = size; > > - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { > + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > /* > * Netfront requires there to be some data in the head > * buffer. > */ > - BUG_ON(*head); > + BUG_ON(*first); > > meta = get_next_rx_buffer(vif, npo); > } > @@ -529,10 +537,10 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > } > > /* Leave a gap for the GSO descriptor. */ > - if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > + if (*first && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > vif->rx.req_cons++; > > - *head = 0; /* There must be something in this buffer now. */ > + *first = 0; /* There must be something in this buffer now. */ > > } > } > @@ -558,7 +566,7 @@ static int netbk_gop_skb(struct sk_buff *skb, > struct xen_netif_rx_request *req; > struct netbk_rx_meta *meta; > unsigned char *data; > - int head = 1; > + int first = 1; > int old_meta_prod; > > old_meta_prod = npo->meta_prod; > @@ -594,16 +602,16 @@ static int netbk_gop_skb(struct sk_buff *skb, > len = skb_tail_pointer(skb) - data; > > netbk_gop_frag_copy(vif, skb, npo, > - virt_to_page(data), len, offset, &head); > + virt_to_page(data), len, offset, 1, &first); > data += len; > } > > for (i = 0; i < nr_frags; i++) { > netbk_gop_frag_copy(vif, skb, npo, > - skb_frag_page(&skb_shinfo(skb)->frags[i]), > - skb_frag_size(&skb_shinfo(skb)->frags[i]), > - skb_shinfo(skb)->frags[i].page_offset, > - &head); > + skb_frag_page(&skb_shinfo(skb)->frags[i]), > + skb_frag_size(&skb_shinfo(skb)->frags[i]), > + skb_shinfo(skb)->frags[i].page_offset, > + 0, &first); > } > > return npo->meta_prod - old_meta_prod; > @@ -661,10 +669,6 @@ static void netbk_add_frag_responses(struct xenvif *vif, int status, > } > } > > -struct skb_cb_overlay { > - int meta_slots_used; > -}; > - > static void xen_netbk_rx_action(struct xen_netbk *netbk) > { > struct xenvif *vif = NULL, *tmp; > @@ -690,19 +694,26 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk) > count = 0; > > while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) { > + RING_IDX old_rx_req_cons; > + > vif = netdev_priv(skb->dev); > nr_frags = skb_shinfo(skb)->nr_frags; > > + old_rx_req_cons = vif->rx.req_cons; > sco = (struct skb_cb_overlay *)skb->cb; > sco->meta_slots_used = netbk_gop_skb(skb, &npo); > > - count += nr_frags + 1; > + count += vif->rx.req_cons - old_rx_req_cons; > > __skb_queue_tail(&rxq, skb); > > + skb = skb_peek(&netbk->rx_queue); > + if (skb == NULL) > + break; > + sco = (struct skb_cb_overlay *) skb->cb; > + > /* Filled the batch queue? */ > - /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */ > - if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE) > + if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE) > break; Using req_cons to count is OK, but since you've already store the number of slots in sco->peek_slots_count before actually queueing the packet, why don't you use that directly? Wei. > } > > -- > 1.7.4.5 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: > On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: > > From: Xi Xiong <xixiong@amazon.com> > > > > [ note: I've just cherry picked this onto net-next, and only compile > > tested. This a RFC only. -msw ] > > > > Should probably rebase it on net.git because it is a bug fix. Let's > worry about that later... > > > Currently the number of RX slots required to transmit a SKB to > > xen-netfront can be miscalculated when an interface uses a MTU larger > > than PAGE_SIZE. If the slot calculation is wrong, xen-netback can > > pause the queue indefinitely or reuse slots. The former manifests as a > > loss of connectivity to the guest (which can be restored by lowering > > the MTU set on the interface). The latter manifests with "Bad grant > > reference" messages from Xen such as: > > > > (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 > > > > and kernel messages within the guest such as: > > > > [ 180.419567] net eth0: Invalid extra type: 112 > > [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 > > [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 > > > > BUG_ON() assertions can also be hit if RX slots are exhausted while > > handling a SKB. > > > > This patch changes xen_netbk_rx_action() to count the number of RX > > slots actually consumed by netbk_gop_skb() instead of using nr_frags + 1. > > This prevents under-counting the number of RX slots consumed when a > > SKB has a large linear buffer. > > > > Additionally, we now store the estimated number of RX slots required > > to handle a SKB in the cb overlay. This value is used to determine if > > the next SKB in the queue can be processed. > > > > Finally, the logic in start_new_rx_buffer() can cause RX slots to be > > wasted when setting up copy grant table operations for SKBs with large > > linear buffers. For example, a SKB with skb_headlen() equal to 8157 > > bytes that starts 64 bytes 64 bytes from the start of the page will > > Duplicated "64 bytes". And this change looks like an improvement not a > bug fix. Probably submit a separate patch for this? > > > consume three RX slots instead of two. This patch changes the "head" > > parameter to netbk_gop_frag_copy() to act as a flag. When set, > > start_new_rx_buffer() will always place as much data as possible into > > each RX slot. > > > > Signed-off-by: Xi Xiong <xixiong@amazon.com> > > Reviewed-by: Matt Wilson <msw@amazon.com> > > [ msw: minor code cleanups, rewrote commit message, adjusted code > > to count RX slots instead of meta structures ] > > Signed-off-by: Matt Wilson <msw@amazon.com> > > Cc: Annie Li <annie.li@oracle.com> > > Cc: Wei Liu <wei.liu2@citrix.com> > > Cc: Ian Campbell <Ian.Campbell@citrix.com> > > Cc: netdev@vger.kernel.org > > Cc: xen-devel@lists.xenproject.org > > --- > > drivers/net/xen-netback/netback.c | 51 ++++++++++++++++++++++-------------- > > 1 files changed, 31 insertions(+), 20 deletions(-) > > > > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > > index 64828de..82dd207 100644 > > --- a/drivers/net/xen-netback/netback.c > > +++ b/drivers/net/xen-netback/netback.c > > @@ -110,6 +110,11 @@ union page_ext { > > void *mapping; > > }; > > > > +struct skb_cb_overlay { > > + int meta_slots_used; > > + int peek_slots_count; > > +}; > > + > > struct xen_netbk { > > wait_queue_head_t wq; > > struct task_struct *task; > > @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > > { > > unsigned int count; > > int i, copy_off; > > + struct skb_cb_overlay *sco; > > > > count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); > > > > @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > > offset = 0; > > } > > } > > + > > + sco = (struct skb_cb_overlay *) skb->cb; > > + sco->peek_slots_count = count; > > return count; > > } > > > > @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, > > } > > > > /* > > - * Set up the grant operations for this fragment. If it's a flipping > > - * interface, we also set up the unmap request from here. > > + * Set up the grant operations for this fragment. > > */ > > static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > struct netrx_pending_operations *npo, > > struct page *page, unsigned long size, > > - unsigned long offset, int *head) > > + unsigned long offset, int head, int *first) > > { > > struct gnttab_copy *copy_gop; > > struct netbk_rx_meta *meta; > > @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > if (bytes > size) > > bytes = size; > > > > - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { > > + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > > /* > > * Netfront requires there to be some data in the head > > * buffer. > > */ > > - BUG_ON(*head); > > + BUG_ON(*first); > > > > meta = get_next_rx_buffer(vif, npo); > > } > > @@ -529,10 +537,10 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > } > > > > /* Leave a gap for the GSO descriptor. */ > > - if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > > + if (*first && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > > vif->rx.req_cons++; > > > > - *head = 0; /* There must be something in this buffer now. */ > > + *first = 0; /* There must be something in this buffer now. */ > > > > } > > } > > @@ -558,7 +566,7 @@ static int netbk_gop_skb(struct sk_buff *skb, > > struct xen_netif_rx_request *req; > > struct netbk_rx_meta *meta; > > unsigned char *data; > > - int head = 1; > > + int first = 1; > > int old_meta_prod; > > > > old_meta_prod = npo->meta_prod; > > @@ -594,16 +602,16 @@ static int netbk_gop_skb(struct sk_buff *skb, > > len = skb_tail_pointer(skb) - data; > > > > netbk_gop_frag_copy(vif, skb, npo, > > - virt_to_page(data), len, offset, &head); > > + virt_to_page(data), len, offset, 1, &first); > > data += len; > > } > > > > for (i = 0; i < nr_frags; i++) { > > netbk_gop_frag_copy(vif, skb, npo, > > - skb_frag_page(&skb_shinfo(skb)->frags[i]), > > - skb_frag_size(&skb_shinfo(skb)->frags[i]), > > - skb_shinfo(skb)->frags[i].page_offset, > > - &head); > > + skb_frag_page(&skb_shinfo(skb)->frags[i]), > > + skb_frag_size(&skb_shinfo(skb)->frags[i]), > > + skb_shinfo(skb)->frags[i].page_offset, > > + 0, &first); > > } > > > > return npo->meta_prod - old_meta_prod; > > @@ -661,10 +669,6 @@ static void netbk_add_frag_responses(struct xenvif *vif, int status, > > } > > } > > > > -struct skb_cb_overlay { > > - int meta_slots_used; > > -}; > > - > > static void xen_netbk_rx_action(struct xen_netbk *netbk) > > { > > struct xenvif *vif = NULL, *tmp; > > @@ -690,19 +694,26 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk) > > count = 0; > > > > while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) { > > + RING_IDX old_rx_req_cons; > > + > > vif = netdev_priv(skb->dev); > > nr_frags = skb_shinfo(skb)->nr_frags; > > > > + old_rx_req_cons = vif->rx.req_cons; > > sco = (struct skb_cb_overlay *)skb->cb; > > sco->meta_slots_used = netbk_gop_skb(skb, &npo); > > > > - count += nr_frags + 1; > > + count += vif->rx.req_cons - old_rx_req_cons; > > > > __skb_queue_tail(&rxq, skb); > > > > + skb = skb_peek(&netbk->rx_queue); > > + if (skb == NULL) > > + break; > > + sco = (struct skb_cb_overlay *) skb->cb; > > + > > /* Filled the batch queue? */ > > - /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */ > > - if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE) > > + if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE) > > break; > > Using req_cons to count is OK, but since you've already store the number > of slots in sco->peek_slots_count before actually queueing the packet, > why don't you use that directly? > Ah, I must be off my head here. I mixed several patches 1) my RFC patch that removes MAX_SKB_FRAGS in RX path, 2) Annie's patch and 3) your patch. The reason that your patches uses req_cons instead of pre-calculated value is, that value returned by xen_netbk_skb_count_slots is actually *wrong* -- that's what Annie tried to fix in her patch. After fixing xen_netbk_skb_count_slots, we would need the above snippet (or the snippet I proposed in my RFC patch) to prevent overruning the ring. So a proper patch to this issue (not couting RX slots correctly causing overrun of the ring) would be the above two aspects combined. Comments? Wei. > > Wei. > > > } > > > > -- > > 1.7.4.5 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013-7-11 3:37, Wei Liu wrote: > On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: >> On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: >>> From: Xi Xiong <xixiong@amazon.com> >>> >>> [ note: I've just cherry picked this onto net-next, and only compile >>> tested. This a RFC only. -msw ] >>> >> Should probably rebase it on net.git because it is a bug fix. Let's >> worry about that later... >> >>> Currently the number of RX slots required to transmit a SKB to >>> xen-netfront can be miscalculated when an interface uses a MTU larger >>> than PAGE_SIZE. If the slot calculation is wrong, xen-netback can >>> pause the queue indefinitely or reuse slots. The former manifests as a >>> loss of connectivity to the guest (which can be restored by lowering >>> the MTU set on the interface). The latter manifests with "Bad grant >>> reference" messages from Xen such as: >>> >>> (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 >>> >>> and kernel messages within the guest such as: >>> >>> [ 180.419567] net eth0: Invalid extra type: 112 >>> [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 >>> [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 >>> >>> BUG_ON() assertions can also be hit if RX slots are exhausted while >>> handling a SKB. >>> >>> This patch changes xen_netbk_rx_action() to count the number of RX >>> slots actually consumed by netbk_gop_skb() instead of using nr_frags + 1. >>> This prevents under-counting the number of RX slots consumed when a >>> SKB has a large linear buffer. >>> >>> Additionally, we now store the estimated number of RX slots required >>> to handle a SKB in the cb overlay. This value is used to determine if >>> the next SKB in the queue can be processed. >>> >>> Finally, the logic in start_new_rx_buffer() can cause RX slots to be >>> wasted when setting up copy grant table operations for SKBs with large >>> linear buffers. For example, a SKB with skb_headlen() equal to 8157 >>> bytes that starts 64 bytes 64 bytes from the start of the page will >> Duplicated "64 bytes". And this change looks like an improvement not a >> bug fix. Probably submit a separate patch for this? >> >>> consume three RX slots instead of two. This patch changes the "head" >>> parameter to netbk_gop_frag_copy() to act as a flag. When set, >>> start_new_rx_buffer() will always place as much data as possible into >>> each RX slot. >>> >>> Signed-off-by: Xi Xiong <xixiong@amazon.com> >>> Reviewed-by: Matt Wilson <msw@amazon.com> >>> [ msw: minor code cleanups, rewrote commit message, adjusted code >>> to count RX slots instead of meta structures ] >>> Signed-off-by: Matt Wilson <msw@amazon.com> >>> Cc: Annie Li <annie.li@oracle.com> >>> Cc: Wei Liu <wei.liu2@citrix.com> >>> Cc: Ian Campbell <Ian.Campbell@citrix.com> >>> Cc: netdev@vger.kernel.org >>> Cc: xen-devel@lists.xenproject.org >>> --- >>> drivers/net/xen-netback/netback.c | 51 ++++++++++++++++++++++-------------- >>> 1 files changed, 31 insertions(+), 20 deletions(-) >>> >>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c >>> index 64828de..82dd207 100644 >>> --- a/drivers/net/xen-netback/netback.c >>> +++ b/drivers/net/xen-netback/netback.c >>> @@ -110,6 +110,11 @@ union page_ext { >>> void *mapping; >>> }; >>> >>> +struct skb_cb_overlay { >>> + int meta_slots_used; >>> + int peek_slots_count; >>> +}; >>> + >>> struct xen_netbk { >>> wait_queue_head_t wq; >>> struct task_struct *task; >>> @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) >>> { >>> unsigned int count; >>> int i, copy_off; >>> + struct skb_cb_overlay *sco; >>> >>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); >>> >>> @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) >>> offset = 0; >>> } >>> } >>> + >>> + sco = (struct skb_cb_overlay *) skb->cb; >>> + sco->peek_slots_count = count; >>> return count; >>> } >>> >>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, >>> } >>> >>> /* >>> - * Set up the grant operations for this fragment. If it's a flipping >>> - * interface, we also set up the unmap request from here. >>> + * Set up the grant operations for this fragment. >>> */ >>> static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, >>> struct netrx_pending_operations *npo, >>> struct page *page, unsigned long size, >>> - unsigned long offset, int *head) >>> + unsigned long offset, int head, int *first) >>> { >>> struct gnttab_copy *copy_gop; >>> struct netbk_rx_meta *meta; >>> @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, >>> if (bytes > size) >>> bytes = size; >>> >>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { >>> + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { >>> /* >>> * Netfront requires there to be some data in the head >>> * buffer. >>> */ >>> - BUG_ON(*head); >>> + BUG_ON(*first); >>> >>> meta = get_next_rx_buffer(vif, npo); >>> } >>> @@ -529,10 +537,10 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, >>> } >>> >>> /* Leave a gap for the GSO descriptor. */ >>> - if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix) >>> + if (*first && skb_shinfo(skb)->gso_size && !vif->gso_prefix) >>> vif->rx.req_cons++; >>> >>> - *head = 0; /* There must be something in this buffer now. */ >>> + *first = 0; /* There must be something in this buffer now. */ >>> >>> } >>> } >>> @@ -558,7 +566,7 @@ static int netbk_gop_skb(struct sk_buff *skb, >>> struct xen_netif_rx_request *req; >>> struct netbk_rx_meta *meta; >>> unsigned char *data; >>> - int head = 1; >>> + int first = 1; >>> int old_meta_prod; >>> >>> old_meta_prod = npo->meta_prod; >>> @@ -594,16 +602,16 @@ static int netbk_gop_skb(struct sk_buff *skb, >>> len = skb_tail_pointer(skb) - data; >>> >>> netbk_gop_frag_copy(vif, skb, npo, >>> - virt_to_page(data), len, offset, &head); >>> + virt_to_page(data), len, offset, 1, &first); >>> data += len; >>> } >>> >>> for (i = 0; i < nr_frags; i++) { >>> netbk_gop_frag_copy(vif, skb, npo, >>> - skb_frag_page(&skb_shinfo(skb)->frags[i]), >>> - skb_frag_size(&skb_shinfo(skb)->frags[i]), >>> - skb_shinfo(skb)->frags[i].page_offset, >>> - &head); >>> + skb_frag_page(&skb_shinfo(skb)->frags[i]), >>> + skb_frag_size(&skb_shinfo(skb)->frags[i]), >>> + skb_shinfo(skb)->frags[i].page_offset, >>> + 0, &first); >>> } >>> >>> return npo->meta_prod - old_meta_prod; >>> @@ -661,10 +669,6 @@ static void netbk_add_frag_responses(struct xenvif *vif, int status, >>> } >>> } >>> >>> -struct skb_cb_overlay { >>> - int meta_slots_used; >>> -}; >>> - >>> static void xen_netbk_rx_action(struct xen_netbk *netbk) >>> { >>> struct xenvif *vif = NULL, *tmp; >>> @@ -690,19 +694,26 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk) >>> count = 0; >>> >>> while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) { >>> + RING_IDX old_rx_req_cons; >>> + >>> vif = netdev_priv(skb->dev); >>> nr_frags = skb_shinfo(skb)->nr_frags; >>> >>> + old_rx_req_cons = vif->rx.req_cons; >>> sco = (struct skb_cb_overlay *)skb->cb; >>> sco->meta_slots_used = netbk_gop_skb(skb, &npo); >>> >>> - count += nr_frags + 1; >>> + count += vif->rx.req_cons - old_rx_req_cons; >>> >>> __skb_queue_tail(&rxq, skb); >>> >>> + skb = skb_peek(&netbk->rx_queue); >>> + if (skb == NULL) >>> + break; >>> + sco = (struct skb_cb_overlay *) skb->cb; >>> + >>> /* Filled the batch queue? */ >>> - /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */ >>> - if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE) >>> + if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE) >>> break; >> Using req_cons to count is OK, but since you've already store the number >> of slots in sco->peek_slots_count before actually queueing the packet, >> why don't you use that directly? >> > Ah, I must be off my head here. I mixed several patches 1) my RFC patch > that removes MAX_SKB_FRAGS in RX path, 2) Annie's patch and 3) your > patch. > > The reason that your patches uses req_cons instead of pre-calculated > value is, that value returned by xen_netbk_skb_count_slots is actually > *wrong* -- that's what Annie tried to fix in her patch. > > After fixing xen_netbk_skb_count_slots, we would need the above snippet > (or the snippet I proposed in my RFC patch) to prevent overruning the > ring. > > So a proper patch to this issue (not couting RX slots correctly causing > overrun of the ring) would be the above two aspects combined. > > Comments? I agree, two patches looks fine. xen_netbk_skb_count_slots returns wrong value, this could be fixed by my patch. protection from overrunning the ring, this could be implemented by Wei's/Matt's patch. Thanks Annie > > > Wei. > >> Wei. >> >>> } >>> >>> -- >>> 1.7.4.5 > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: > On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: > > On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: > > > From: Xi Xiong <xixiong@amazon.com> > > > > > > [ note: I've just cherry picked this onto net-next, and only compile > > > tested. This a RFC only. -msw ] > > > > > > > Should probably rebase it on net.git because it is a bug fix. Let's > > worry about that later... *nod* > > > Currently the number of RX slots required to transmit a SKB to > > > xen-netfront can be miscalculated when an interface uses a MTU larger > > > than PAGE_SIZE. If the slot calculation is wrong, xen-netback can > > > pause the queue indefinitely or reuse slots. The former manifests as a > > > loss of connectivity to the guest (which can be restored by lowering > > > the MTU set on the interface). The latter manifests with "Bad grant > > > reference" messages from Xen such as: > > > > > > (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 > > > > > > and kernel messages within the guest such as: > > > > > > [ 180.419567] net eth0: Invalid extra type: 112 > > > [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 > > > [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 > > > > > > BUG_ON() assertions can also be hit if RX slots are exhausted while > > > handling a SKB. > > > > > > This patch changes xen_netbk_rx_action() to count the number of RX > > > slots actually consumed by netbk_gop_skb() instead of using nr_frags + 1. > > > This prevents under-counting the number of RX slots consumed when a > > > SKB has a large linear buffer. > > > > > > Additionally, we now store the estimated number of RX slots required > > > to handle a SKB in the cb overlay. This value is used to determine if > > > the next SKB in the queue can be processed. > > > > > > Finally, the logic in start_new_rx_buffer() can cause RX slots to be > > > wasted when setting up copy grant table operations for SKBs with large > > > linear buffers. For example, a SKB with skb_headlen() equal to 8157 > > > bytes that starts 64 bytes 64 bytes from the start of the page will > > > > Duplicated "64 bytes". And this change looks like an improvement not a > > bug fix. Probably submit a separate patch for this? Argh, I knew it was in there somewhere (since you pointed it out in Dubin :-). Maybe it could be a separate patch. I think the description is also a bit confusing. I'll work on rewording it. > > > consume three RX slots instead of two. This patch changes the "head" > > > parameter to netbk_gop_frag_copy() to act as a flag. When set, > > > start_new_rx_buffer() will always place as much data as possible into > > > each RX slot. > > > > > > Signed-off-by: Xi Xiong <xixiong@amazon.com> > > > Reviewed-by: Matt Wilson <msw@amazon.com> > > > [ msw: minor code cleanups, rewrote commit message, adjusted code > > > to count RX slots instead of meta structures ] > > > Signed-off-by: Matt Wilson <msw@amazon.com> > > > Cc: Annie Li <annie.li@oracle.com> > > > Cc: Wei Liu <wei.liu2@citrix.com> > > > Cc: Ian Campbell <Ian.Campbell@citrix.com> > > > Cc: netdev@vger.kernel.org > > > Cc: xen-devel@lists.xenproject.org > > > --- > > > drivers/net/xen-netback/netback.c | 51 ++++++++++++++++++++++-------------- > > > 1 files changed, 31 insertions(+), 20 deletions(-) > > > > > > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c > > > index 64828de..82dd207 100644 > > > --- a/drivers/net/xen-netback/netback.c > > > +++ b/drivers/net/xen-netback/netback.c > > > @@ -110,6 +110,11 @@ union page_ext { > > > void *mapping; > > > }; > > > > > > +struct skb_cb_overlay { > > > + int meta_slots_used; > > > + int peek_slots_count; > > > +}; > > > + > > > struct xen_netbk { > > > wait_queue_head_t wq; > > > struct task_struct *task; > > > @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > > > { > > > unsigned int count; > > > int i, copy_off; > > > + struct skb_cb_overlay *sco; > > > > > > count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); > > > > > > @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) > > > offset = 0; > > > } > > > } > > > + > > > + sco = (struct skb_cb_overlay *) skb->cb; > > > + sco->peek_slots_count = count; > > > return count; > > > } > > > > > > @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, > > > } > > > > > > /* > > > - * Set up the grant operations for this fragment. If it's a flipping > > > - * interface, we also set up the unmap request from here. > > > + * Set up the grant operations for this fragment. > > > */ > > > static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > > struct netrx_pending_operations *npo, > > > struct page *page, unsigned long size, > > > - unsigned long offset, int *head) > > > + unsigned long offset, int head, int *first) > > > { > > > struct gnttab_copy *copy_gop; > > > struct netbk_rx_meta *meta; > > > @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > > if (bytes > size) > > > bytes = size; > > > > > > - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { > > > + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > > > /* > > > * Netfront requires there to be some data in the head > > > * buffer. > > > */ > > > - BUG_ON(*head); > > > + BUG_ON(*first); > > > > > > meta = get_next_rx_buffer(vif, npo); > > > } > > > @@ -529,10 +537,10 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, > > > } > > > > > > /* Leave a gap for the GSO descriptor. */ > > > - if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > > > + if (*first && skb_shinfo(skb)->gso_size && !vif->gso_prefix) > > > vif->rx.req_cons++; > > > > > > - *head = 0; /* There must be something in this buffer now. */ > > > + *first = 0; /* There must be something in this buffer now. */ > > > > > > } > > > } > > > @@ -558,7 +566,7 @@ static int netbk_gop_skb(struct sk_buff *skb, > > > struct xen_netif_rx_request *req; > > > struct netbk_rx_meta *meta; > > > unsigned char *data; > > > - int head = 1; > > > + int first = 1; > > > int old_meta_prod; > > > > > > old_meta_prod = npo->meta_prod; > > > @@ -594,16 +602,16 @@ static int netbk_gop_skb(struct sk_buff *skb, > > > len = skb_tail_pointer(skb) - data; > > > > > > netbk_gop_frag_copy(vif, skb, npo, > > > - virt_to_page(data), len, offset, &head); > > > + virt_to_page(data), len, offset, 1, &first); > > > data += len; > > > } > > > > > > for (i = 0; i < nr_frags; i++) { > > > netbk_gop_frag_copy(vif, skb, npo, > > > - skb_frag_page(&skb_shinfo(skb)->frags[i]), > > > - skb_frag_size(&skb_shinfo(skb)->frags[i]), > > > - skb_shinfo(skb)->frags[i].page_offset, > > > - &head); > > > + skb_frag_page(&skb_shinfo(skb)->frags[i]), > > > + skb_frag_size(&skb_shinfo(skb)->frags[i]), > > > + skb_shinfo(skb)->frags[i].page_offset, > > > + 0, &first); > > > } > > > > > > return npo->meta_prod - old_meta_prod; > > > @@ -661,10 +669,6 @@ static void netbk_add_frag_responses(struct xenvif *vif, int status, > > > } > > > } > > > > > > -struct skb_cb_overlay { > > > - int meta_slots_used; > > > -}; > > > - > > > static void xen_netbk_rx_action(struct xen_netbk *netbk) > > > { > > > struct xenvif *vif = NULL, *tmp; > > > @@ -690,19 +694,26 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk) > > > count = 0; > > > > > > while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) { > > > + RING_IDX old_rx_req_cons; > > > + > > > vif = netdev_priv(skb->dev); > > > nr_frags = skb_shinfo(skb)->nr_frags; > > > > > > + old_rx_req_cons = vif->rx.req_cons; > > > sco = (struct skb_cb_overlay *)skb->cb; > > > sco->meta_slots_used = netbk_gop_skb(skb, &npo); > > > > > > - count += nr_frags + 1; > > > + count += vif->rx.req_cons - old_rx_req_cons; > > > > > > __skb_queue_tail(&rxq, skb); > > > > > > + skb = skb_peek(&netbk->rx_queue); > > > + if (skb == NULL) > > > + break; > > > + sco = (struct skb_cb_overlay *) skb->cb; > > > + > > > /* Filled the batch queue? */ > > > - /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */ > > > - if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE) > > > + if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE) > > > break; > > > > Using req_cons to count is OK, but since you've already store the number > > of slots in sco->peek_slots_count before actually queueing the packet, > > why don't you use that directly? > > > > Ah, I must be off my head here. I mixed several patches 1) my RFC patch > that removes MAX_SKB_FRAGS in RX path, 2) Annie's patch and 3) your > patch. Yes, I wanted to get this out since we're talking about multiple changes in similar areas. > The reason that your patches uses req_cons instead of pre-calculated > value is, that value returned by xen_netbk_skb_count_slots is actually > *wrong* -- that's what Annie tried to fix in her patch. Yes and no. With this patch, the xen_netbk_count_skb_slots() is now correct. xen_netbk_count_skb_slots() was under-counting when slots were inefficiently consumed. With this patch they match. Since we've had trouble with the counting in the past, I felt like using the "real" number of slots here was safer and future-proof. > After fixing xen_netbk_skb_count_slots, we would need the above snippet > (or the snippet I proposed in my RFC patch) to prevent overruning the > ring. Agreed. > So a proper patch to this issue (not couting RX slots correctly causing > overrun of the ring) would be the above two aspects combined. Yes, I think so. > Comments? I think that this patch addresses the problem more completely. Annie? See also the thread from last August: http://lists.xen.org/archives/html/xen-devel/2012-12/msg00274.html --msw -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013-7-11 13:14, Matt Wilson wrote: > On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: >> On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: >>> On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: >>>> From: Xi Xiong <xixiong@amazon.com> >>>> >>>> [ note: I've just cherry picked this onto net-next, and only compile >>>> tested. This a RFC only. -msw ] >>>> >>> Should probably rebase it on net.git because it is a bug fix. Let's >>> worry about that later... > *nod* > >>>> Currently the number of RX slots required to transmit a SKB to >>>> xen-netfront can be miscalculated when an interface uses a MTU larger >>>> than PAGE_SIZE. If the slot calculation is wrong, xen-netback can >>>> pause the queue indefinitely or reuse slots. The former manifests as a >>>> loss of connectivity to the guest (which can be restored by lowering >>>> the MTU set on the interface). The latter manifests with "Bad grant >>>> reference" messages from Xen such as: >>>> >>>> (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 >>>> >>>> and kernel messages within the guest such as: >>>> >>>> [ 180.419567] net eth0: Invalid extra type: 112 >>>> [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 >>>> [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 >>>> >>>> BUG_ON() assertions can also be hit if RX slots are exhausted while >>>> handling a SKB. >>>> >>>> This patch changes xen_netbk_rx_action() to count the number of RX >>>> slots actually consumed by netbk_gop_skb() instead of using nr_frags + 1. >>>> This prevents under-counting the number of RX slots consumed when a >>>> SKB has a large linear buffer. >>>> >>>> Additionally, we now store the estimated number of RX slots required >>>> to handle a SKB in the cb overlay. This value is used to determine if >>>> the next SKB in the queue can be processed. >>>> >>>> Finally, the logic in start_new_rx_buffer() can cause RX slots to be >>>> wasted when setting up copy grant table operations for SKBs with large >>>> linear buffers. For example, a SKB with skb_headlen() equal to 8157 >>>> bytes that starts 64 bytes 64 bytes from the start of the page will >>> Duplicated "64 bytes". And this change looks like an improvement not a >>> bug fix. Probably submit a separate patch for this? > Argh, I knew it was in there somewhere (since you pointed it out in > Dubin :-). > > Maybe it could be a separate patch. I think the description is also a > bit confusing. I'll work on rewording it. > >>>> consume three RX slots instead of two. This patch changes the "head" >>>> parameter to netbk_gop_frag_copy() to act as a flag. When set, >>>> start_new_rx_buffer() will always place as much data as possible into >>>> each RX slot. >>>> >>>> Signed-off-by: Xi Xiong <xixiong@amazon.com> >>>> Reviewed-by: Matt Wilson <msw@amazon.com> >>>> [ msw: minor code cleanups, rewrote commit message, adjusted code >>>> to count RX slots instead of meta structures ] >>>> Signed-off-by: Matt Wilson <msw@amazon.com> >>>> Cc: Annie Li <annie.li@oracle.com> >>>> Cc: Wei Liu <wei.liu2@citrix.com> >>>> Cc: Ian Campbell <Ian.Campbell@citrix.com> >>>> Cc: netdev@vger.kernel.org >>>> Cc: xen-devel@lists.xenproject.org >>>> --- >>>> drivers/net/xen-netback/netback.c | 51 ++++++++++++++++++++++-------------- >>>> 1 files changed, 31 insertions(+), 20 deletions(-) >>>> >>>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c >>>> index 64828de..82dd207 100644 >>>> --- a/drivers/net/xen-netback/netback.c >>>> +++ b/drivers/net/xen-netback/netback.c >>>> @@ -110,6 +110,11 @@ union page_ext { >>>> void *mapping; >>>> }; >>>> >>>> +struct skb_cb_overlay { >>>> + int meta_slots_used; >>>> + int peek_slots_count; >>>> +}; >>>> + >>>> struct xen_netbk { >>>> wait_queue_head_t wq; >>>> struct task_struct *task; >>>> @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) >>>> { >>>> unsigned int count; >>>> int i, copy_off; >>>> + struct skb_cb_overlay *sco; >>>> >>>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); >>>> >>>> @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) >>>> offset = 0; >>>> } >>>> } >>>> + >>>> + sco = (struct skb_cb_overlay *) skb->cb; >>>> + sco->peek_slots_count = count; >>>> return count; >>>> } >>>> >>>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, >>>> } >>>> >>>> /* >>>> - * Set up the grant operations for this fragment. If it's a flipping >>>> - * interface, we also set up the unmap request from here. >>>> + * Set up the grant operations for this fragment. >>>> */ >>>> static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, >>>> struct netrx_pending_operations *npo, >>>> struct page *page, unsigned long size, >>>> - unsigned long offset, int *head) >>>> + unsigned long offset, int head, int *first) >>>> { >>>> struct gnttab_copy *copy_gop; >>>> struct netbk_rx_meta *meta; >>>> @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, >>>> if (bytes > size) >>>> bytes = size; >>>> >>>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { >>>> + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { head is always 1 here when processing the header data, so it is impossible to start a new buffer for header data with larger header size, and get_next_rx_buffer is never called. I assume this would not work well for skb with larger header data size. Have you run network test with this patch? >>>> /* >>>> * Netfront requires there to be some data in the head >>>> * buffer. >>>> */ >>>> - BUG_ON(*head); >>>> + BUG_ON(*first); >>>> >>>> meta = get_next_rx_buffer(vif, npo); >>>> } snip... >>>> Comments? > I think that this patch addresses the problem more completely. Annie? See my comments above, I am curious whether the header data is processed correctly.:-) Thanks Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 10, 2013 at 10:14:43PM -0700, Matt Wilson wrote: [...] > Yes, I wanted to get this out since we're talking about multiple > changes in similar areas. > > > The reason that your patches uses req_cons instead of pre-calculated > > value is, that value returned by xen_netbk_skb_count_slots is actually > > *wrong* -- that's what Annie tried to fix in her patch. > > Yes and no. With this patch, the xen_netbk_count_skb_slots() is now > correct. xen_netbk_count_skb_slots() was under-counting when slots > were inefficiently consumed. With this patch they match. > This is worth mentioning in the commit message IMHO. > Since we've had trouble with the counting in the past, I felt like > using the "real" number of slots here was safer and future-proof. > Fair enough. Worth a comment in the code. > > After fixing xen_netbk_skb_count_slots, we would need the above snippet > > (or the snippet I proposed in my RFC patch) to prevent overruning the > > ring. > > Agreed. > > > So a proper patch to this issue (not couting RX slots correctly causing > > overrun of the ring) would be the above two aspects combined. > > Yes, I think so. > > > Comments? > > I think that this patch addresses the problem more completely. Annie? > > See also the thread from last August: > http://lists.xen.org/archives/html/xen-devel/2012-12/msg00274.html > So now it seems that "turning head in start_new_rx_buffer to flag" part should also be in the patch as it's actually a fix to match counting in both functions. The side effect of this change is "improving efficiency of the ring". This would also worth mentioning in the commit message IMHO. Wei. > --msw -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013-7-11 14:01, annie li wrote: > > On 2013-7-11 13:14, Matt Wilson wrote: >> On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: >>> On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: >>>> On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: >>>>> From: Xi Xiong <xixiong@amazon.com> >>>>> >>>>> [ note: I've just cherry picked this onto net-next, and only compile >>>>> tested. This a RFC only. -msw ] >>>>> >>>> Should probably rebase it on net.git because it is a bug fix. Let's >>>> worry about that later... >> *nod* >> >>>>> Currently the number of RX slots required to transmit a SKB to >>>>> xen-netfront can be miscalculated when an interface uses a MTU larger >>>>> than PAGE_SIZE. If the slot calculation is wrong, xen-netback can >>>>> pause the queue indefinitely or reuse slots. The former manifests >>>>> as a >>>>> loss of connectivity to the guest (which can be restored by lowering >>>>> the MTU set on the interface). The latter manifests with "Bad grant >>>>> reference" messages from Xen such as: >>>>> >>>>> (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 >>>>> >>>>> and kernel messages within the guest such as: >>>>> >>>>> [ 180.419567] net eth0: Invalid extra type: 112 >>>>> [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 >>>>> [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 >>>>> >>>>> BUG_ON() assertions can also be hit if RX slots are exhausted while >>>>> handling a SKB. >>>>> >>>>> This patch changes xen_netbk_rx_action() to count the number of RX >>>>> slots actually consumed by netbk_gop_skb() instead of using >>>>> nr_frags + 1. >>>>> This prevents under-counting the number of RX slots consumed when a >>>>> SKB has a large linear buffer. >>>>> >>>>> Additionally, we now store the estimated number of RX slots required >>>>> to handle a SKB in the cb overlay. This value is used to determine if >>>>> the next SKB in the queue can be processed. >>>>> >>>>> Finally, the logic in start_new_rx_buffer() can cause RX slots to be >>>>> wasted when setting up copy grant table operations for SKBs with >>>>> large >>>>> linear buffers. For example, a SKB with skb_headlen() equal to 8157 >>>>> bytes that starts 64 bytes 64 bytes from the start of the page will >>>> Duplicated "64 bytes". And this change looks like an improvement not a >>>> bug fix. Probably submit a separate patch for this? >> Argh, I knew it was in there somewhere (since you pointed it out in >> Dubin :-). >> >> Maybe it could be a separate patch. I think the description is also a >> bit confusing. I'll work on rewording it. >> >>>>> consume three RX slots instead of two. This patch changes the "head" >>>>> parameter to netbk_gop_frag_copy() to act as a flag. When set, >>>>> start_new_rx_buffer() will always place as much data as possible into >>>>> each RX slot. >>>>> >>>>> Signed-off-by: Xi Xiong <xixiong@amazon.com> >>>>> Reviewed-by: Matt Wilson <msw@amazon.com> >>>>> [ msw: minor code cleanups, rewrote commit message, adjusted code >>>>> to count RX slots instead of meta structures ] >>>>> Signed-off-by: Matt Wilson <msw@amazon.com> >>>>> Cc: Annie Li <annie.li@oracle.com> >>>>> Cc: Wei Liu <wei.liu2@citrix.com> >>>>> Cc: Ian Campbell <Ian.Campbell@citrix.com> >>>>> Cc: netdev@vger.kernel.org >>>>> Cc: xen-devel@lists.xenproject.org >>>>> --- >>>>> drivers/net/xen-netback/netback.c | 51 >>>>> ++++++++++++++++++++++-------------- >>>>> 1 files changed, 31 insertions(+), 20 deletions(-) >>>>> >>>>> diff --git a/drivers/net/xen-netback/netback.c >>>>> b/drivers/net/xen-netback/netback.c >>>>> index 64828de..82dd207 100644 >>>>> --- a/drivers/net/xen-netback/netback.c >>>>> +++ b/drivers/net/xen-netback/netback.c >>>>> @@ -110,6 +110,11 @@ union page_ext { >>>>> void *mapping; >>>>> }; >>>>> +struct skb_cb_overlay { >>>>> + int meta_slots_used; >>>>> + int peek_slots_count; >>>>> +}; >>>>> + >>>>> struct xen_netbk { >>>>> wait_queue_head_t wq; >>>>> struct task_struct *task; >>>>> @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct >>>>> xenvif *vif, struct sk_buff *skb) >>>>> { >>>>> unsigned int count; >>>>> int i, copy_off; >>>>> + struct skb_cb_overlay *sco; >>>>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); >>>>> @@ -411,6 +417,9 @@ unsigned int >>>>> xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) >>>>> offset = 0; >>>>> } >>>>> } >>>>> + >>>>> + sco = (struct skb_cb_overlay *) skb->cb; >>>>> + sco->peek_slots_count = count; >>>>> return count; >>>>> } >>>>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta >>>>> *get_next_rx_buffer(struct xenvif *vif, >>>>> } >>>>> /* >>>>> - * Set up the grant operations for this fragment. If it's a flipping >>>>> - * interface, we also set up the unmap request from here. >>>>> + * Set up the grant operations for this fragment. >>>>> */ >>>>> static void netbk_gop_frag_copy(struct xenvif *vif, struct >>>>> sk_buff *skb, >>>>> struct netrx_pending_operations *npo, >>>>> struct page *page, unsigned long size, >>>>> - unsigned long offset, int *head) >>>>> + unsigned long offset, int head, int *first) >>>>> { >>>>> struct gnttab_copy *copy_gop; >>>>> struct netbk_rx_meta *meta; >>>>> @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct >>>>> xenvif *vif, struct sk_buff *skb, >>>>> if (bytes > size) >>>>> bytes = size; >>>>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { >>>>> + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > > head is always 1 here when processing the header data, so it is > impossible to start a new buffer for header data with larger header > size, and get_next_rx_buffer is never called. I assume this would not > work well for skb with larger header data size. Have you run network > test with this patch? Sorry, I forgot the offset == MAX_BUFFER_OFFSET case and misunderstand your patch, please ignore my last comments. Your patch keeps the original DIV_ROUND_UP and changes the mechanism in netbk_gop_frag_copy to make slots same with xen_netbk_count_skb_slots. All Roads Lead to Rome!:-) Thanks Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jul 11, 2013 at 09:52:52PM +0800, annie li wrote: > > On 2013-7-11 14:01, annie li wrote: > > > >On 2013-7-11 13:14, Matt Wilson wrote: > >>On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: > >>>On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: > >>>>On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: > >>>>>From: Xi Xiong <xixiong@amazon.com> > >>>>> > >>>>>[ note: I've just cherry picked this onto net-next, and only compile > >>>>> tested. This a RFC only. -msw ] > >>>>> > >>>>Should probably rebase it on net.git because it is a bug fix. Let's > >>>>worry about that later... > >>*nod* > >> > >>>>>Currently the number of RX slots required to transmit a SKB to > >>>>>xen-netfront can be miscalculated when an interface uses a MTU larger > >>>>>than PAGE_SIZE. If the slot calculation is wrong, xen-netback can > >>>>>pause the queue indefinitely or reuse slots. The former > >>>>>manifests as a > >>>>>loss of connectivity to the guest (which can be restored by lowering > >>>>>the MTU set on the interface). The latter manifests with "Bad grant > >>>>>reference" messages from Xen such as: > >>>>> > >>>>>(XEN) grant_table.c:1797:d0 Bad grant reference 264241157 > >>>>> > >>>>>and kernel messages within the guest such as: > >>>>> > >>>>>[ 180.419567] net eth0: Invalid extra type: 112 > >>>>>[ 180.868620] net eth0: rx->offset: 0, size: 4294967295 > >>>>>[ 180.868629] net eth0: rx->offset: 0, size: 4294967295 > >>>>> > >>>>>BUG_ON() assertions can also be hit if RX slots are exhausted while > >>>>>handling a SKB. > >>>>> > >>>>>This patch changes xen_netbk_rx_action() to count the number of RX > >>>>>slots actually consumed by netbk_gop_skb() instead of > >>>>>using nr_frags + 1. > >>>>>This prevents under-counting the number of RX slots consumed when a > >>>>>SKB has a large linear buffer. > >>>>> > >>>>>Additionally, we now store the estimated number of RX slots required > >>>>>to handle a SKB in the cb overlay. This value is used to determine if > >>>>>the next SKB in the queue can be processed. > >>>>> > >>>>>Finally, the logic in start_new_rx_buffer() can cause RX slots to be > >>>>>wasted when setting up copy grant table operations for > >>>>>SKBs with large > >>>>>linear buffers. For example, a SKB with skb_headlen() equal to 8157 > >>>>>bytes that starts 64 bytes 64 bytes from the start of the page will > >>>>Duplicated "64 bytes". And this change looks like an improvement not a > >>>>bug fix. Probably submit a separate patch for this? > >>Argh, I knew it was in there somewhere (since you pointed it out in > >>Dubin :-). > >> > >>Maybe it could be a separate patch. I think the description is also a > >>bit confusing. I'll work on rewording it. > >> > >>>>>consume three RX slots instead of two. This patch changes the "head" > >>>>>parameter to netbk_gop_frag_copy() to act as a flag. When set, > >>>>>start_new_rx_buffer() will always place as much data as possible into > >>>>>each RX slot. > >>>>> > >>>>>Signed-off-by: Xi Xiong <xixiong@amazon.com> > >>>>>Reviewed-by: Matt Wilson <msw@amazon.com> > >>>>>[ msw: minor code cleanups, rewrote commit message, adjusted code > >>>>> to count RX slots instead of meta structures ] > >>>>>Signed-off-by: Matt Wilson <msw@amazon.com> > >>>>>Cc: Annie Li <annie.li@oracle.com> > >>>>>Cc: Wei Liu <wei.liu2@citrix.com> > >>>>>Cc: Ian Campbell <Ian.Campbell@citrix.com> > >>>>>Cc: netdev@vger.kernel.org > >>>>>Cc: xen-devel@lists.xenproject.org > >>>>>--- > >>>>> drivers/net/xen-netback/netback.c | 51 > >>>>>++++++++++++++++++++++-------------- > >>>>> 1 files changed, 31 insertions(+), 20 deletions(-) > >>>>> > >>>>>diff --git a/drivers/net/xen-netback/netback.c > >>>>>b/drivers/net/xen-netback/netback.c > >>>>>index 64828de..82dd207 100644 > >>>>>--- a/drivers/net/xen-netback/netback.c > >>>>>+++ b/drivers/net/xen-netback/netback.c > >>>>>@@ -110,6 +110,11 @@ union page_ext { > >>>>> void *mapping; > >>>>> }; > >>>>> +struct skb_cb_overlay { > >>>>>+ int meta_slots_used; > >>>>>+ int peek_slots_count; > >>>>>+}; > >>>>>+ > >>>>> struct xen_netbk { > >>>>> wait_queue_head_t wq; > >>>>> struct task_struct *task; > >>>>>@@ -370,6 +375,7 @@ unsigned int > >>>>>xen_netbk_count_skb_slots(struct xenvif *vif, struct > >>>>>sk_buff *skb) > >>>>> { > >>>>> unsigned int count; > >>>>> int i, copy_off; > >>>>>+ struct skb_cb_overlay *sco; > >>>>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); > >>>>> @@ -411,6 +417,9 @@ unsigned int > >>>>>xen_netbk_count_skb_slots(struct xenvif *vif, struct > >>>>>sk_buff *skb) > >>>>> offset = 0; > >>>>> } > >>>>> } > >>>>>+ > >>>>>+ sco = (struct skb_cb_overlay *) skb->cb; > >>>>>+ sco->peek_slots_count = count; > >>>>> return count; > >>>>> } > >>>>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta > >>>>>*get_next_rx_buffer(struct xenvif *vif, > >>>>> } > >>>>> /* > >>>>>- * Set up the grant operations for this fragment. If it's a flipping > >>>>>- * interface, we also set up the unmap request from here. > >>>>>+ * Set up the grant operations for this fragment. > >>>>> */ > >>>>> static void netbk_gop_frag_copy(struct xenvif *vif, > >>>>>struct sk_buff *skb, > >>>>> struct netrx_pending_operations *npo, > >>>>> struct page *page, unsigned long size, > >>>>>- unsigned long offset, int *head) > >>>>>+ unsigned long offset, int head, int *first) > >>>>> { > >>>>> struct gnttab_copy *copy_gop; > >>>>> struct netbk_rx_meta *meta; > >>>>>@@ -479,12 +487,12 @@ static void > >>>>>netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff > >>>>>*skb, > >>>>> if (bytes > size) > >>>>> bytes = size; > >>>>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { > >>>>>+ if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > > > >head is always 1 here when processing the header data, so it is > >impossible to start a new buffer for header data with larger > >header size, and get_next_rx_buffer is never called. I assume this > >would not work well for skb with larger header data size. Have you > >run network test with this patch? > > Sorry, I forgot the offset == MAX_BUFFER_OFFSET case and > misunderstand your patch, please ignore my last comments. Your patch > keeps the original DIV_ROUND_UP and changes the mechanism in > netbk_gop_frag_copy to make slots same with > xen_netbk_count_skb_slots. All Roads Lead to Rome!:-) > Actually I'm now in favor of Matt's approach as it a) fix the bug, b) make efficient use of the ring. Annie, Ian, what's your opinion? Wei. > Thanks > Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013-7-12 16:49, Wei Liu wrote: > On Thu, Jul 11, 2013 at 09:52:52PM +0800, annie li wrote: >> On 2013-7-11 14:01, annie li wrote: >>> On 2013-7-11 13:14, Matt Wilson wrote: >>>> On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: >>>>> On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: >>>>>> On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: >>>>>>> From: Xi Xiong <xixiong@amazon.com> >>>>>>> >>>>>>> [ note: I've just cherry picked this onto net-next, and only compile >>>>>>> tested. This a RFC only. -msw ] >>>>>>> >>>>>> Should probably rebase it on net.git because it is a bug fix. Let's >>>>>> worry about that later... >>>> *nod* >>>> >>>>>>> Currently the number of RX slots required to transmit a SKB to >>>>>>> xen-netfront can be miscalculated when an interface uses a MTU larger >>>>>>> than PAGE_SIZE. If the slot calculation is wrong, xen-netback can >>>>>>> pause the queue indefinitely or reuse slots. The former >>>>>>> manifests as a >>>>>>> loss of connectivity to the guest (which can be restored by lowering >>>>>>> the MTU set on the interface). The latter manifests with "Bad grant >>>>>>> reference" messages from Xen such as: >>>>>>> >>>>>>> (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 >>>>>>> >>>>>>> and kernel messages within the guest such as: >>>>>>> >>>>>>> [ 180.419567] net eth0: Invalid extra type: 112 >>>>>>> [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 >>>>>>> [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 >>>>>>> >>>>>>> BUG_ON() assertions can also be hit if RX slots are exhausted while >>>>>>> handling a SKB. >>>>>>> >>>>>>> This patch changes xen_netbk_rx_action() to count the number of RX >>>>>>> slots actually consumed by netbk_gop_skb() instead of >>>>>>> using nr_frags + 1. >>>>>>> This prevents under-counting the number of RX slots consumed when a >>>>>>> SKB has a large linear buffer. >>>>>>> >>>>>>> Additionally, we now store the estimated number of RX slots required >>>>>>> to handle a SKB in the cb overlay. This value is used to determine if >>>>>>> the next SKB in the queue can be processed. >>>>>>> >>>>>>> Finally, the logic in start_new_rx_buffer() can cause RX slots to be >>>>>>> wasted when setting up copy grant table operations for >>>>>>> SKBs with large >>>>>>> linear buffers. For example, a SKB with skb_headlen() equal to 8157 >>>>>>> bytes that starts 64 bytes 64 bytes from the start of the page will >>>>>> Duplicated "64 bytes". And this change looks like an improvement not a >>>>>> bug fix. Probably submit a separate patch for this? >>>> Argh, I knew it was in there somewhere (since you pointed it out in >>>> Dubin :-). >>>> >>>> Maybe it could be a separate patch. I think the description is also a >>>> bit confusing. I'll work on rewording it. >>>> >>>>>>> consume three RX slots instead of two. This patch changes the "head" >>>>>>> parameter to netbk_gop_frag_copy() to act as a flag. When set, >>>>>>> start_new_rx_buffer() will always place as much data as possible into >>>>>>> each RX slot. >>>>>>> >>>>>>> Signed-off-by: Xi Xiong <xixiong@amazon.com> >>>>>>> Reviewed-by: Matt Wilson <msw@amazon.com> >>>>>>> [ msw: minor code cleanups, rewrote commit message, adjusted code >>>>>>> to count RX slots instead of meta structures ] >>>>>>> Signed-off-by: Matt Wilson <msw@amazon.com> >>>>>>> Cc: Annie Li <annie.li@oracle.com> >>>>>>> Cc: Wei Liu <wei.liu2@citrix.com> >>>>>>> Cc: Ian Campbell <Ian.Campbell@citrix.com> >>>>>>> Cc: netdev@vger.kernel.org >>>>>>> Cc: xen-devel@lists.xenproject.org >>>>>>> --- >>>>>>> drivers/net/xen-netback/netback.c | 51 >>>>>>> ++++++++++++++++++++++-------------- >>>>>>> 1 files changed, 31 insertions(+), 20 deletions(-) >>>>>>> >>>>>>> diff --git a/drivers/net/xen-netback/netback.c >>>>>>> b/drivers/net/xen-netback/netback.c >>>>>>> index 64828de..82dd207 100644 >>>>>>> --- a/drivers/net/xen-netback/netback.c >>>>>>> +++ b/drivers/net/xen-netback/netback.c >>>>>>> @@ -110,6 +110,11 @@ union page_ext { >>>>>>> void *mapping; >>>>>>> }; >>>>>>> +struct skb_cb_overlay { >>>>>>> + int meta_slots_used; >>>>>>> + int peek_slots_count; >>>>>>> +}; >>>>>>> + >>>>>>> struct xen_netbk { >>>>>>> wait_queue_head_t wq; >>>>>>> struct task_struct *task; >>>>>>> @@ -370,6 +375,7 @@ unsigned int >>>>>>> xen_netbk_count_skb_slots(struct xenvif *vif, struct >>>>>>> sk_buff *skb) >>>>>>> { >>>>>>> unsigned int count; >>>>>>> int i, copy_off; >>>>>>> + struct skb_cb_overlay *sco; >>>>>>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); >>>>>>> @@ -411,6 +417,9 @@ unsigned int >>>>>>> xen_netbk_count_skb_slots(struct xenvif *vif, struct >>>>>>> sk_buff *skb) >>>>>>> offset = 0; >>>>>>> } >>>>>>> } >>>>>>> + >>>>>>> + sco = (struct skb_cb_overlay *) skb->cb; >>>>>>> + sco->peek_slots_count = count; >>>>>>> return count; >>>>>>> } >>>>>>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta >>>>>>> *get_next_rx_buffer(struct xenvif *vif, >>>>>>> } >>>>>>> /* >>>>>>> - * Set up the grant operations for this fragment. If it's a flipping >>>>>>> - * interface, we also set up the unmap request from here. >>>>>>> + * Set up the grant operations for this fragment. >>>>>>> */ >>>>>>> static void netbk_gop_frag_copy(struct xenvif *vif, >>>>>>> struct sk_buff *skb, >>>>>>> struct netrx_pending_operations *npo, >>>>>>> struct page *page, unsigned long size, >>>>>>> - unsigned long offset, int *head) >>>>>>> + unsigned long offset, int head, int *first) >>>>>>> { >>>>>>> struct gnttab_copy *copy_gop; >>>>>>> struct netbk_rx_meta *meta; >>>>>>> @@ -479,12 +487,12 @@ static void >>>>>>> netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff >>>>>>> *skb, >>>>>>> if (bytes > size) >>>>>>> bytes = size; >>>>>>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { >>>>>>> + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { >>> head is always 1 here when processing the header data, so it is >>> impossible to start a new buffer for header data with larger >>> header size, and get_next_rx_buffer is never called. I assume this >>> would not work well for skb with larger header data size. Have you >>> run network test with this patch? >> Sorry, I forgot the offset == MAX_BUFFER_OFFSET case and >> misunderstand your patch, please ignore my last comments. Your patch >> keeps the original DIV_ROUND_UP and changes the mechanism in >> netbk_gop_frag_copy to make slots same with >> xen_netbk_count_skb_slots. All Roads Lead to Rome!:-) >> > Actually I'm now in favor of Matt's approach as it a) fix the bug, b) > make efficient use of the ring. > > Annie, Ian, what's your opinion? Me too. Looks his approach not only fix this bug, but also saves the ring usage for header data, and this is good. Combining my patch with his is not a good idea, so I think we can use his patch. Thanks Annie > > > Wei. > >> Thanks >> Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013-7-11 13:14, Matt Wilson wrote:
> I think that this patch addresses the problem more completely. Annie?
Agree, it is better to take your patch. Would you like to go forward
with it? This issue is obvious and easy to be hit with larger MTU size.
Thanks
Annie
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On Tue, Jul 16, 2013 at 06:08:03PM +0800, annie li wrote: > > On 2013-7-11 13:14, Matt Wilson wrote: > >I think that this patch addresses the problem more completely. Annie? > > Agree, it is better to take your patch. Would you like to go forward > with it? This issue is obvious and easy to be hit with larger MTU > size. > I'm going to be on vacation tomorrow. Matt, feel free to add my Acked-by to your patch. Wei. > Thanks > Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jul 16, 2013 at 11:27:19AM +0100, Wei Liu wrote: > On Tue, Jul 16, 2013 at 06:08:03PM +0800, annie li wrote: > > > > On 2013-7-11 13:14, Matt Wilson wrote: > > >I think that this patch addresses the problem more completely. Annie? > > > > Agree, it is better to take your patch. Would you like to go forward > > with it? This issue is obvious and easy to be hit with larger MTU > > size. > > > > I'm going to be on vacation tomorrow. Matt, feel free to add my Acked-by to > your patch. Thanks, Wei. I'm on vacation now and I'll return to the office tomorrow. Please accept my apologies for the delay. I should have time to clean up a few things with this patch (no functional changes) and post a final version this week. --msw > Wei. > > > Thanks > > Annie -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2013-07-12 at 17:19 +0800, annie li wrote: > On 2013-7-12 16:49, Wei Liu wrote: > > On Thu, Jul 11, 2013 at 09:52:52PM +0800, annie li wrote: > >> On 2013-7-11 14:01, annie li wrote: > >>> On 2013-7-11 13:14, Matt Wilson wrote: > >>>> On Wed, Jul 10, 2013 at 08:37:03PM +0100, Wei Liu wrote: > >>>>> On Wed, Jul 10, 2013 at 09:13:33AM +0100, Wei Liu wrote: > >>>>>> On Tue, Jul 09, 2013 at 10:40:59PM +0000, Matt Wilson wrote: > >>>>>>> From: Xi Xiong <xixiong@amazon.com> > >>>>>>> > >>>>>>> [ note: I've just cherry picked this onto net-next, and only compile > >>>>>>> tested. This a RFC only. -msw ] > >>>>>>> > >>>>>> Should probably rebase it on net.git because it is a bug fix. Let's > >>>>>> worry about that later... > >>>> *nod* > >>>> > >>>>>>> Currently the number of RX slots required to transmit a SKB to > >>>>>>> xen-netfront can be miscalculated when an interface uses a MTU larger > >>>>>>> than PAGE_SIZE. If the slot calculation is wrong, xen-netback can > >>>>>>> pause the queue indefinitely or reuse slots. The former > >>>>>>> manifests as a > >>>>>>> loss of connectivity to the guest (which can be restored by lowering > >>>>>>> the MTU set on the interface). The latter manifests with "Bad grant > >>>>>>> reference" messages from Xen such as: > >>>>>>> > >>>>>>> (XEN) grant_table.c:1797:d0 Bad grant reference 264241157 > >>>>>>> > >>>>>>> and kernel messages within the guest such as: > >>>>>>> > >>>>>>> [ 180.419567] net eth0: Invalid extra type: 112 > >>>>>>> [ 180.868620] net eth0: rx->offset: 0, size: 4294967295 > >>>>>>> [ 180.868629] net eth0: rx->offset: 0, size: 4294967295 > >>>>>>> > >>>>>>> BUG_ON() assertions can also be hit if RX slots are exhausted while > >>>>>>> handling a SKB. > >>>>>>> > >>>>>>> This patch changes xen_netbk_rx_action() to count the number of RX > >>>>>>> slots actually consumed by netbk_gop_skb() instead of > >>>>>>> using nr_frags + 1. > >>>>>>> This prevents under-counting the number of RX slots consumed when a > >>>>>>> SKB has a large linear buffer. > >>>>>>> > >>>>>>> Additionally, we now store the estimated number of RX slots required > >>>>>>> to handle a SKB in the cb overlay. This value is used to determine if > >>>>>>> the next SKB in the queue can be processed. > >>>>>>> > >>>>>>> Finally, the logic in start_new_rx_buffer() can cause RX slots to be > >>>>>>> wasted when setting up copy grant table operations for > >>>>>>> SKBs with large > >>>>>>> linear buffers. For example, a SKB with skb_headlen() equal to 8157 > >>>>>>> bytes that starts 64 bytes 64 bytes from the start of the page will > >>>>>> Duplicated "64 bytes". And this change looks like an improvement not a > >>>>>> bug fix. Probably submit a separate patch for this? > >>>> Argh, I knew it was in there somewhere (since you pointed it out in > >>>> Dubin :-). > >>>> > >>>> Maybe it could be a separate patch. I think the description is also a > >>>> bit confusing. I'll work on rewording it. > >>>> > >>>>>>> consume three RX slots instead of two. This patch changes the "head" > >>>>>>> parameter to netbk_gop_frag_copy() to act as a flag. When set, > >>>>>>> start_new_rx_buffer() will always place as much data as possible into > >>>>>>> each RX slot. > >>>>>>> > >>>>>>> Signed-off-by: Xi Xiong <xixiong@amazon.com> > >>>>>>> Reviewed-by: Matt Wilson <msw@amazon.com> > >>>>>>> [ msw: minor code cleanups, rewrote commit message, adjusted code > >>>>>>> to count RX slots instead of meta structures ] > >>>>>>> Signed-off-by: Matt Wilson <msw@amazon.com> > >>>>>>> Cc: Annie Li <annie.li@oracle.com> > >>>>>>> Cc: Wei Liu <wei.liu2@citrix.com> > >>>>>>> Cc: Ian Campbell <Ian.Campbell@citrix.com> > >>>>>>> Cc: netdev@vger.kernel.org > >>>>>>> Cc: xen-devel@lists.xenproject.org > >>>>>>> --- > >>>>>>> drivers/net/xen-netback/netback.c | 51 > >>>>>>> ++++++++++++++++++++++-------------- > >>>>>>> 1 files changed, 31 insertions(+), 20 deletions(-) > >>>>>>> > >>>>>>> diff --git a/drivers/net/xen-netback/netback.c > >>>>>>> b/drivers/net/xen-netback/netback.c > >>>>>>> index 64828de..82dd207 100644 > >>>>>>> --- a/drivers/net/xen-netback/netback.c > >>>>>>> +++ b/drivers/net/xen-netback/netback.c > >>>>>>> @@ -110,6 +110,11 @@ union page_ext { > >>>>>>> void *mapping; > >>>>>>> }; > >>>>>>> +struct skb_cb_overlay { > >>>>>>> + int meta_slots_used; > >>>>>>> + int peek_slots_count; > >>>>>>> +}; > >>>>>>> + > >>>>>>> struct xen_netbk { > >>>>>>> wait_queue_head_t wq; > >>>>>>> struct task_struct *task; > >>>>>>> @@ -370,6 +375,7 @@ unsigned int > >>>>>>> xen_netbk_count_skb_slots(struct xenvif *vif, struct > >>>>>>> sk_buff *skb) > >>>>>>> { > >>>>>>> unsigned int count; > >>>>>>> int i, copy_off; > >>>>>>> + struct skb_cb_overlay *sco; > >>>>>>> count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); > >>>>>>> @@ -411,6 +417,9 @@ unsigned int > >>>>>>> xen_netbk_count_skb_slots(struct xenvif *vif, struct > >>>>>>> sk_buff *skb) > >>>>>>> offset = 0; > >>>>>>> } > >>>>>>> } > >>>>>>> + > >>>>>>> + sco = (struct skb_cb_overlay *) skb->cb; > >>>>>>> + sco->peek_slots_count = count; > >>>>>>> return count; > >>>>>>> } > >>>>>>> @@ -443,13 +452,12 @@ static struct netbk_rx_meta > >>>>>>> *get_next_rx_buffer(struct xenvif *vif, > >>>>>>> } > >>>>>>> /* > >>>>>>> - * Set up the grant operations for this fragment. If it's a flipping > >>>>>>> - * interface, we also set up the unmap request from here. > >>>>>>> + * Set up the grant operations for this fragment. > >>>>>>> */ > >>>>>>> static void netbk_gop_frag_copy(struct xenvif *vif, > >>>>>>> struct sk_buff *skb, > >>>>>>> struct netrx_pending_operations *npo, > >>>>>>> struct page *page, unsigned long size, > >>>>>>> - unsigned long offset, int *head) > >>>>>>> + unsigned long offset, int head, int *first) > >>>>>>> { > >>>>>>> struct gnttab_copy *copy_gop; > >>>>>>> struct netbk_rx_meta *meta; > >>>>>>> @@ -479,12 +487,12 @@ static void > >>>>>>> netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff > >>>>>>> *skb, > >>>>>>> if (bytes > size) > >>>>>>> bytes = size; > >>>>>>> - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { > >>>>>>> + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { > >>> head is always 1 here when processing the header data, so it is > >>> impossible to start a new buffer for header data with larger > >>> header size, and get_next_rx_buffer is never called. I assume this > >>> would not work well for skb with larger header data size. Have you > >>> run network test with this patch? > >> Sorry, I forgot the offset == MAX_BUFFER_OFFSET case and > >> misunderstand your patch, please ignore my last comments. Your patch > >> keeps the original DIV_ROUND_UP and changes the mechanism in > >> netbk_gop_frag_copy to make slots same with > >> xen_netbk_count_skb_slots. All Roads Lead to Rome!:-) > >> > > Actually I'm now in favor of Matt's approach as it a) fix the bug, b) > > make efficient use of the ring. > > > > Annie, Ian, what's your opinion? > > Me too. Looks his approach not only fix this bug, but also saves the > ring usage for header data, and this is good. > Combining my patch with his is not a good idea, so I think we can use > his patch. Sounds good to me. I didn't review the patch in <1373409659-22383-1-git-send-email-msw@amazon.com> in much detail because I think we are expecting a respin with some of Wei & Annie's comment addressed? If I'm wrong and I've just missed that posting please cluebat me. Ian. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 64828de..82dd207 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -110,6 +110,11 @@ union page_ext { void *mapping; }; +struct skb_cb_overlay { + int meta_slots_used; + int peek_slots_count; +}; + struct xen_netbk { wait_queue_head_t wq; struct task_struct *task; @@ -370,6 +375,7 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) { unsigned int count; int i, copy_off; + struct skb_cb_overlay *sco; count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE); @@ -411,6 +417,9 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb) offset = 0; } } + + sco = (struct skb_cb_overlay *) skb->cb; + sco->peek_slots_count = count; return count; } @@ -443,13 +452,12 @@ static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif, } /* - * Set up the grant operations for this fragment. If it's a flipping - * interface, we also set up the unmap request from here. + * Set up the grant operations for this fragment. */ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, struct netrx_pending_operations *npo, struct page *page, unsigned long size, - unsigned long offset, int *head) + unsigned long offset, int head, int *first) { struct gnttab_copy *copy_gop; struct netbk_rx_meta *meta; @@ -479,12 +487,12 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, if (bytes > size) bytes = size; - if (start_new_rx_buffer(npo->copy_off, bytes, *head)) { + if (start_new_rx_buffer(npo->copy_off, bytes, head)) { /* * Netfront requires there to be some data in the head * buffer. */ - BUG_ON(*head); + BUG_ON(*first); meta = get_next_rx_buffer(vif, npo); } @@ -529,10 +537,10 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, } /* Leave a gap for the GSO descriptor. */ - if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix) + if (*first && skb_shinfo(skb)->gso_size && !vif->gso_prefix) vif->rx.req_cons++; - *head = 0; /* There must be something in this buffer now. */ + *first = 0; /* There must be something in this buffer now. */ } } @@ -558,7 +566,7 @@ static int netbk_gop_skb(struct sk_buff *skb, struct xen_netif_rx_request *req; struct netbk_rx_meta *meta; unsigned char *data; - int head = 1; + int first = 1; int old_meta_prod; old_meta_prod = npo->meta_prod; @@ -594,16 +602,16 @@ static int netbk_gop_skb(struct sk_buff *skb, len = skb_tail_pointer(skb) - data; netbk_gop_frag_copy(vif, skb, npo, - virt_to_page(data), len, offset, &head); + virt_to_page(data), len, offset, 1, &first); data += len; } for (i = 0; i < nr_frags; i++) { netbk_gop_frag_copy(vif, skb, npo, - skb_frag_page(&skb_shinfo(skb)->frags[i]), - skb_frag_size(&skb_shinfo(skb)->frags[i]), - skb_shinfo(skb)->frags[i].page_offset, - &head); + skb_frag_page(&skb_shinfo(skb)->frags[i]), + skb_frag_size(&skb_shinfo(skb)->frags[i]), + skb_shinfo(skb)->frags[i].page_offset, + 0, &first); } return npo->meta_prod - old_meta_prod; @@ -661,10 +669,6 @@ static void netbk_add_frag_responses(struct xenvif *vif, int status, } } -struct skb_cb_overlay { - int meta_slots_used; -}; - static void xen_netbk_rx_action(struct xen_netbk *netbk) { struct xenvif *vif = NULL, *tmp; @@ -690,19 +694,26 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk) count = 0; while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) { + RING_IDX old_rx_req_cons; + vif = netdev_priv(skb->dev); nr_frags = skb_shinfo(skb)->nr_frags; + old_rx_req_cons = vif->rx.req_cons; sco = (struct skb_cb_overlay *)skb->cb; sco->meta_slots_used = netbk_gop_skb(skb, &npo); - count += nr_frags + 1; + count += vif->rx.req_cons - old_rx_req_cons; __skb_queue_tail(&rxq, skb); + skb = skb_peek(&netbk->rx_queue); + if (skb == NULL) + break; + sco = (struct skb_cb_overlay *) skb->cb; + /* Filled the batch queue? */ - /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */ - if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE) + if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE) break; }