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39 lines
1.2 KiB
Diff
39 lines
1.2 KiB
Diff
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From a9b204d1564702b704ad6fe74f10a102c7b87ba3 Mon Sep 17 00:00:00 2001
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From: Eric Dumazet <edumazet@google.com>
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Date: Sat, 3 Dec 2016 11:14:53 -0800
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Subject: [PATCH 04/10] tcp: tsq: avoid one atomic in tcp_wfree()
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Under high load, tcp_wfree() has an atomic operation trying
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to schedule a tasklet over and over.
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We can schedule it only if our per cpu list was empty.
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Signed-off-by: Eric Dumazet <edumazet@google.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/ipv4/tcp_output.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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--- a/net/ipv4/tcp_output.c
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+++ b/net/ipv4/tcp_output.c
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@@ -880,6 +880,7 @@ void tcp_wfree(struct sk_buff *skb)
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for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) {
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struct tsq_tasklet *tsq;
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+ bool empty;
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if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
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goto out;
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@@ -892,8 +893,10 @@ void tcp_wfree(struct sk_buff *skb)
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/* queue this socket to tasklet queue */
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local_irq_save(flags);
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tsq = this_cpu_ptr(&tsq_tasklet);
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+ empty = list_empty(&tsq->head);
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list_add(&tp->tsq_node, &tsq->head);
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- tasklet_schedule(&tsq->tasklet);
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+ if (empty)
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+ tasklet_schedule(&tsq->tasklet);
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local_irq_restore(flags);
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return;
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}
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