From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: netdev@vger.kernel.org, john.ogness@linutronix.de, thomas@glanzmann.de
Subject: Re: [PATCH] tcp: tsq: fix nonagle handling
Date: Mon, 10 Feb 2014 15:24:16 -0800 (PST) [thread overview]
Message-ID: <20140210.152416.1707361996340298057.davem@davemloft.net> (raw)
In-Reply-To: <1392000011.6615.15.camel@edumazet-glaptop2.roam.corp.google.com>
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Sun, 09 Feb 2014 18:40:11 -0800
> From: John Ogness <john.ogness@linutronix.de>
>
> Commit 46d3ceabd8d9 ("tcp: TCP Small Queues") introduced a possible
> regression for applications using TCP_NODELAY.
>
> If TCP session is throttled because of tsq, we should consult
> tp->nonagle when TX completion is done and allow us to send additional
> segment, especially if this segment is not a full MSS.
> Otherwise this segment is sent after an RTO.
>
> [edumazet] : Cooked the changelog, added another fix about testing
> sk_wmem_alloc twice because TX completion can happen right before
> setting TSQ_THROTTLED bit.
>
> This problem is particularly visible with recent auto corking,
> but might also be triggered with low tcp_limit_output_bytes
> values or NIC drivers delaying TX completion by hundred of usec,
> and very low rtt.
>
> Thomas Glanzmann for example reported an iscsi regression, caused
> by tcp auto corking making this bug quite visible.
>
> Fixes: 46d3ceabd8d9 ("tcp: TCP Small Queues")
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Thomas Glanzmann <thomas@glanzmann.de>
Applied and queued up for -stable, thanks!
prev parent reply other threads:[~2014-02-10 23:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-10 2:40 [PATCH] tcp: tsq: fix nonagle handling Eric Dumazet
2014-02-10 23:24 ` David Miller [this message]
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