netdev - Re: [PATCH net-next 0/3] tcp: take a bit more care of backlog stress

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Message-Id: <20181123.112516.1009412686662405132.davem@davemloft.net>
Date:   Fri, 23 Nov 2018 11:25:16 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, jean-louis@...ond.be, ncardwell@...gle.com,
        ycheng@...gle.com, eric.dumazet@...il.com
Subject: Re: [PATCH net-next 0/3] tcp: take a bit more care of backlog
 stress

From: Eric Dumazet <edumazet@...gle.com>
Date: Wed, 21 Nov 2018 09:52:37 -0800

> While working on the SACK compression issue Jean-Louis Dupond
> reported, we found that his linux box was suffering very hard
> from tail drops on the socket backlog queue, because the opposite
> TCP stack was ont implementing latest RFC recommendations.
> 
> First patch is a cleanup
> 
> Second patch is attempting coalescing when a new packet must
> be added to the backlog queue. Cooking bigger skbs helps
> to keep backlog list smaller and speeds its handling when
> user thread finally releases the socket lock.
> 
> Third patch is implementing head drop as a last resort.
> Head drops are generally better for optimal TCP behavior.

My impression is that patch #2 needs some fixes in order to not
lose dupacks.  So there will be a respin of this.

Thanks.