linux-kernel - Re: Major network performance regression in 3.7

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Date:	Sun, 06 Jan 2013 09:10:55 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Major network performance regression in 3.7

On Sun, 2013-01-06 at 17:44 +0100, Willy Tarreau wrote:
> On Sun, Jan 06, 2013 at 08:39:53AM -0800, Eric Dumazet wrote:
> > Hmm, I'll have to check if this really can be reverted without hurting
> > vmsplice() again.
> 
> Looking at the code I've been wondering whether we shouldn't transform
> the condition to perform the push if we can't push more segments, but
> I don't know what to rely on. It would be something like this :
> 
>        if (copied &&
>           (!(flags & MSG_SENDPAGE_NOTLAST) || cant_push_more))
>                 tcp_push(sk, flags, mss_now, tp->nonagle);

Good point !

Maybe the following fix then ?


diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1ca2536..7ba0717 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -941,8 +941,10 @@ out:
 	return copied;
 
 do_error:
-	if (copied)
+	if (copied) {
+		flags &= ~MSG_SENDPAGE_NOTLAST;
 		goto out;
+	}
 out_err:
 	return sk_stream_error(sk, flags, err);
 }


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