From ebda37c27d0c768947e9b058332d7ea798210cf8 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 6 May 2010 23:51:21 +0000
Subject: [PATCH] rps: avoid one atomic in enqueue_to_backlog
If CONFIG_SMP=y, then we own a queue spinlock, we can avoid the atomic
test_and_set_bit() from napi_schedule_prep().
We now have same number of atomic ops per netif_rx() calls than with
pre-RPS kernel.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/dev.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 988e42912e72..cdcb9cbedf41 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2432,8 +2432,10 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
return NET_RX_SUCCESS;
}
- /* Schedule NAPI for backlog device */
- if (napi_schedule_prep(&sd->backlog)) {
+ /* Schedule NAPI for backlog device
+ * We can use non atomic operation since we own the queue lock
+ */
+ if (!__test_and_set_bit(NAPI_STATE_SCHED, &sd->backlog.state)) {
if (!rps_ipi_queued(sd))
____napi_schedule(sd, &sd->backlog);
}
--
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