Commit 821eba96 authored Mar 28, 2023 by Eric Dumazet Committed by Paolo Abeni Mar 30, 2023

net: optimize napi_schedule_rps()

Based on initial patch from Jason Xing.

Idea is to not raise NET_RX_SOFTIRQ from napi_schedule_rps()
when we queued a packet into another cpu backlog.

We can do this only in the context of us being called indirectly
from net_rx_action(), to have the guarantee our rps_ipi_list
will be processed before we exit from net_rx_action().

Link: https://lore.kernel.org/lkml/20230325152417.5403-1-kerneljasonxing@gmail.com/


Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Tested-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

parent c59647c0

net/core/dev.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -4587,8 +4587,6 @@ static void trigger_rx_softirq(void *data)
		*
		* - If this is another cpu queue, link it to our rps_ipi_list,
		* and make sure we will process rps_ipi_list from net_rx_action().
		* As we do not know yet if we are called from net_rx_action(),
		* we have to raise NET_RX_SOFTIRQ. This might change in the future.
		*
		* - If this is our own queue, NAPI schedule our backlog.
		* Note that this also raises NET_RX_SOFTIRQ.
		@@ -4602,6 +4600,10 @@ static void napi_schedule_rps(struct softnet_data *sd)
		sd->rps_ipi_next = mysd->rps_ipi_list;
		mysd->rps_ipi_list = sd;

		/* If not called from net_rx_action()
		* we have to raise NET_RX_SOFTIRQ.
		*/
		if (!mysd->in_net_rx_action)
		__raise_softirq_irqoff(NET_RX_SOFTIRQ);
		return;
		}