From b2ea46fe236ae02d845f94cf984cbc1786870333 Mon Sep 17 00:00:00 2001 From: Pavel Kubelun Date: Tue, 25 Jul 2017 03:57:31 -0400 Subject: generic: net: tcp: backport tcp tx performance patches An overall throughput gain of 22 % for heavy TCP use over a single TX queue. Original patchset comment https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v4.13&id=3f4888adae7c1619b990d98a9b967536f71822b8 Signed-off-by: Pavel Kubelun --- ...-remove-one-locked-operation-in-tcp_wfree.patch | 48 ++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch (limited to 'target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch') diff --git a/target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch b/target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch new file mode 100644 index 0000000000..914be607e7 --- /dev/null +++ b/target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch @@ -0,0 +1,48 @@ +From 408f0a6c21e124cc4f6c7aa370b38aa47e55428d Mon Sep 17 00:00:00 2001 +From: Eric Dumazet +Date: Sat, 3 Dec 2016 11:14:51 -0800 +Subject: [PATCH 02/10] tcp: tsq: remove one locked operation in tcp_wfree() + +Instead of atomically clear TSQ_THROTTLED and atomically set TSQ_QUEUED +bits, use one cmpxchg() to perform a single locked operation. + +Since the following patch will also set TCP_TSQ_DEFERRED here, +this cmpxchg() will make this addition free. + +Signed-off-by: Eric Dumazet +Signed-off-by: David S. Miller +--- + net/ipv4/tcp_output.c | 13 ++++++++++--- + 1 file changed, 10 insertions(+), 3 deletions(-) + +--- a/net/ipv4/tcp_output.c ++++ b/net/ipv4/tcp_output.c +@@ -860,6 +860,7 @@ void tcp_wfree(struct sk_buff *skb) + { + struct sock *sk = skb->sk; + struct tcp_sock *tp = tcp_sk(sk); ++ unsigned long flags, nval, oval; + int wmem; + + /* Keep one reference on sk_wmem_alloc. +@@ -877,11 +878,17 @@ void tcp_wfree(struct sk_buff *skb) + if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) + goto out; + +- if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && +- !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) { +- unsigned long flags; ++ for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) { + struct tsq_tasklet *tsq; + ++ if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED)) ++ goto out; ++ ++ nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED; ++ nval = cmpxchg(&tp->tsq_flags, oval, nval); ++ if (nval != oval) ++ continue; ++ + /* queue this socket to tasklet queue */ + local_irq_save(flags); + tsq = this_cpu_ptr(&tsq_tasklet); -- cgit v1.2.3