diff mbox

[net-next,1/4] net: allow large number of rx queues

Message ID 1416327778-17716-2-git-send-email-pagupta@redhat.com
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Pankaj Gupta Nov. 18, 2014, 4:22 p.m. UTC 
netif_alloc_rx_queues() uses kcalloc() to allocate memory
for "struct netdev_queue *_rx" array.
If we are doing large rx queue allocation kcalloc() might
fail, so this patch does a fallback to vzalloc().
Similar implementation is done for tx queue allocation in
netif_alloc_netdev_queues().

We avoid failure of high order memory allocation
with the help of vzalloc(), this allows us to do large
rx and tx queue allocation which in turn helps us to
increase the number of queues in tun.

As vmalloc() adds overhead on a critical network path,
__GFP_REPEAT flag is used with kzalloc() to do this fallback
only when really needed.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Gibson <dgibson@redhat.com>
---
 net/core/dev.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

Comments

Cong Wang Nov. 18, 2014, 8:29 p.m. UTC | #1 
On Tue, Nov 18, 2014 at 8:22 AM, Pankaj Gupta <pagupta@redhat.com> wrote:
>
> As vmalloc() adds overhead on a critical network path,
> __GFP_REPEAT flag is used with kzalloc() to do this fallback
> only when really needed.
>

Are you sure we need __GFP_REPEAT? We have vmalloc() as
fallback of kmalloc() in many places of networking (grep kvfree),
none of those I checked has this flag set.
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Pankaj Gupta Nov. 20, 2014, 4:31 p.m. UTC | #2 
> On Tue, Nov 18, 2014 at 8:22 AM, Pankaj Gupta <pagupta@redhat.com> wrote:
> >
> > As vmalloc() adds overhead on a critical network path,
> > __GFP_REPEAT flag is used with kzalloc() to do this fallback
> > only when really needed.
> >
> 
> Are you sure we need __GFP_REPEAT? We have vmalloc() as
> fallback of kmalloc() in many places of networking (grep kvfree),
> none of those I checked has this flag set.

Its there in netif_alloc_netdev_queues() function in same file.
Also, I found it some other places as well.
I think its good to have.
> 
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diff mbox

Patch

diff --git a/net/core/dev.c b/net/core/dev.c
index e916ba8..abe9560 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6059,17 +6059,25 @@  void netif_stacked_transfer_operstate(const struct net_device *rootdev,
 EXPORT_SYMBOL(netif_stacked_transfer_operstate);
 
 #ifdef CONFIG_SYSFS
+static void netif_free_rx_queues(struct net_device *dev)
+{
+	kvfree(dev->_rx);
+}
+
 static int netif_alloc_rx_queues(struct net_device *dev)
 {
 	unsigned int i, count = dev->num_rx_queues;
 	struct netdev_rx_queue *rx;
+	size_t sz = count * sizeof(*rx);
 
 	BUG_ON(count < 1);
 
-	rx = kcalloc(count, sizeof(struct netdev_rx_queue), GFP_KERNEL);
-	if (!rx)
-		return -ENOMEM;
-
+	rx = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
+	if (!rx) {
+		rx = vzalloc(sz);
+		if (!rx)
+			return -ENOMEM;
+	}
 	dev->_rx = rx;
 
 	for (i = 0; i < count; i++)
@@ -6698,9 +6706,8 @@  void free_netdev(struct net_device *dev)
 
 	netif_free_tx_queues(dev);
 #ifdef CONFIG_SYSFS
-	kfree(dev->_rx);
+	netif_free_rx_queues(dev);
 #endif
-
 	kfree(rcu_dereference_protected(dev->ingress_queue, 1));
 
 	/* Flush device addresses */