netdev - Re: TCPBacklogDrops during aggressive bursts of traffic

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Message-ID: <1337355955.15044.24.camel@kjm-desktop.uk.level5networks.com>
Date:	Fri, 18 May 2012 16:45:51 +0100
From:	Kieran Mansley <kmansley@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>, <netdev@...r.kernel.org>
Subject: Re: TCPBacklogDrops during aggressive bursts of traffic

On Thu, 2012-05-17 at 18:37 +0200, Eric Dumazet wrote:
> 
> Hmm, I was not suggesting running production servers with this
> setting, only do an experiment.

OK.  I've found a more reliable way to reproduce it (use MSG_WAITALL to
make the recv call wait till the socket buffer will be more full) and
tried with the tcp_adv_win_scale to -2.  It's hard to make any confident
assertions about the impact of it, but if it does change the behaviour
it is a small change.  There are certainly still plenty of drops with
that setting.

> With net-next and tcp coalescing, I no longer have TCPBacklogDrops /
> collapses, but I dont have sfc card/driver. 

I'll try that.

Kieran

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