| Message ID | 1389184918-42790-1-git-send-email-paul.durrant@citrix.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Wed, Jan 08, 2014 at 12:41:58PM +0000, Paul Durrant wrote: > The recent patch to improve guest receive side flow control (ca2f09f2) had a > slight flaw in the wait condition for the vif thread in that any remaining > skbs in the guest receive side netback internal queue would prevent the > thread from sleeping. An unresponsive frontend can lead to a permanently > non-empty internal queue and thus the thread will spin. In this case the > thread should really sleep until the frontend becomes responsive again. > > This patch adds an extra flag to the vif which is set if the shared ring > is full and cleared when skbs are drained into the shared ring. Thus, > if the thread runs, finds the shared ring full and can make no progress the > flag remains set. If the flag remains set then the thread will sleep, > regardless of a non-empty queue, until the next event from the frontend. > > Signed-off-by: Paul Durrant <paul.durrant@citrix.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Cc: Ian Campbell <ian.campbell@citrix.com> > Cc: David Vrabel <david.vrabel@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com> Thanks Wei. -- 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
From: Wei Liu <wei.liu2@citrix.com> Date: Wed, 8 Jan 2014 19:37:16 +0000 > On Wed, Jan 08, 2014 at 12:41:58PM +0000, Paul Durrant wrote: >> The recent patch to improve guest receive side flow control (ca2f09f2) had a >> slight flaw in the wait condition for the vif thread in that any remaining >> skbs in the guest receive side netback internal queue would prevent the >> thread from sleeping. An unresponsive frontend can lead to a permanently >> non-empty internal queue and thus the thread will spin. In this case the >> thread should really sleep until the frontend becomes responsive again. >> >> This patch adds an extra flag to the vif which is set if the shared ring >> is full and cleared when skbs are drained into the shared ring. Thus, >> if the thread runs, finds the shared ring full and can make no progress the >> flag remains set. If the flag remains set then the thread will sleep, >> regardless of a non-empty queue, until the next event from the frontend. >> >> Signed-off-by: Paul Durrant <paul.durrant@citrix.com> >> Cc: Wei Liu <wei.liu2@citrix.com> >> Cc: Ian Campbell <ian.campbell@citrix.com> >> Cc: David Vrabel <david.vrabel@citrix.com> > > Acked-by: Wei Liu <wei.liu2@citrix.com> Applied. -- 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/common.h b/drivers/net/xen-netback/common.h index c955fc3..4c76bcb 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -143,6 +143,7 @@ struct xenvif { char rx_irq_name[IFNAMSIZ+4]; /* DEVNAME-rx */ struct xen_netif_rx_back_ring rx; struct sk_buff_head rx_queue; + bool rx_queue_stopped; /* Set when the RX interrupt is triggered by the frontend. * The worker thread may need to wake the queue. */ diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 4f81ac0..2738563 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -476,7 +476,8 @@ static void xenvif_rx_action(struct xenvif *vif) int ret; unsigned long offset; struct skb_cb_overlay *sco; - int need_to_notify = 0; + bool need_to_notify = false; + bool ring_full = false; struct netrx_pending_operations npo = { .copy = vif->grant_copy_op, @@ -508,7 +509,8 @@ static void xenvif_rx_action(struct xenvif *vif) /* If the skb may not fit then bail out now */ if (!xenvif_rx_ring_slots_available(vif, max_slots_needed)) { skb_queue_head(&vif->rx_queue, skb); - need_to_notify = 1; + need_to_notify = true; + ring_full = true; break; } @@ -521,6 +523,8 @@ static void xenvif_rx_action(struct xenvif *vif) BUG_ON(npo.meta_prod > ARRAY_SIZE(vif->meta)); + vif->rx_queue_stopped = !npo.copy_prod && ring_full; + if (!npo.copy_prod) goto done; @@ -592,8 +596,7 @@ static void xenvif_rx_action(struct xenvif *vif) RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret); - if (ret) - need_to_notify = 1; + need_to_notify |= !!ret; npo.meta_cons += sco->meta_slots_used; dev_kfree_skb(skb); @@ -1724,7 +1727,8 @@ static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif, static inline int rx_work_todo(struct xenvif *vif) { - return !skb_queue_empty(&vif->rx_queue) || vif->rx_event; + return (!skb_queue_empty(&vif->rx_queue) && !vif->rx_queue_stopped) || + vif->rx_event; } static inline int tx_work_todo(struct xenvif *vif)
The recent patch to improve guest receive side flow control (ca2f09f2) had a slight flaw in the wait condition for the vif thread in that any remaining skbs in the guest receive side netback internal queue would prevent the thread from sleeping. An unresponsive frontend can lead to a permanently non-empty internal queue and thus the thread will spin. In this case the thread should really sleep until the frontend becomes responsive again. This patch adds an extra flag to the vif which is set if the shared ring is full and cleared when skbs are drained into the shared ring. Thus, if the thread runs, finds the shared ring full and can make no progress the flag remains set. If the flag remains set then the thread will sleep, regardless of a non-empty queue, until the next event from the frontend. Signed-off-by: Paul Durrant <paul.durrant@citrix.com> Cc: Wei Liu <wei.liu2@citrix.com> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: David Vrabel <david.vrabel@citrix.com> --- v2: - Use bool for ring_full - Convert need_to_notify to bool for consistency drivers/net/xen-netback/common.h | 1 + drivers/net/xen-netback/netback.c | 14 +++++++++----- 2 files changed, 10 insertions(+), 5 deletions(-)