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38 lines
1.3 KiB
Diff
38 lines
1.3 KiB
Diff
From 75eefc6c59fd2c5f1ab95a3a113c217237d12a31 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 11:14:54 -0800
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Subject: [PATCH 05/10] tcp: tsq: add a shortcut in tcp_small_queue_check()
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Always allow the two first skbs in write queue to be sent,
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regardless of sk_wmem_alloc/sk_pacing_rate values.
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This helps a lot in situations where TX completions are delayed either
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because of driver latencies or softirq latencies.
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Test is done with no cache line misses.
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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 | 9 +++++++++
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1 file changed, 9 insertions(+)
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--- a/net/ipv4/tcp_output.c
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+++ b/net/ipv4/tcp_output.c
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@@ -2084,6 +2084,15 @@ static bool tcp_small_queue_check(struct
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limit <<= factor;
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if (atomic_read(&sk->sk_wmem_alloc) > limit) {
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+ /* Always send the 1st or 2nd skb in write queue.
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+ * No need to wait for TX completion to call us back,
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+ * after softirq/tasklet schedule.
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+ * This helps when TX completions are delayed too much.
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+ */
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+ if (skb == sk->sk_write_queue.next ||
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+ skb->prev == sk->sk_write_queue.next)
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+ return false;
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+
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set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags);
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/* It is possible TX completion already happened
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* before we set TSQ_THROTTLED, so we must
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