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rps: avoid one atomic in enqueue_to_backlog

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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>
This commit is contained in:
Eric Dumazet 2010-05-06 23:51:21 +00:00 committed by David S. Miller
parent 3f78d1f210
commit ebda37c27d
1 changed files with 4 additions and 2 deletions
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6
net/core/dev.c
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@ -2432,8 +2432,10 @@ enqueue:
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);
}