netdev - Re: [PATCH] net: gro: selective flush of packets

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Message-Id: <20121008.145216.988125819977620502.davem@davemloft.net>
Date:	Mon, 08 Oct 2012 14:52:16 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	herbert@...dor.apana.org.au, netdev@...r.kernel.org,
	jesse@...ira.com, therbert@...gle.com, ycheng@...gle.com
Subject: Re: [PATCH] net: gro: selective flush of packets

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 06 Oct 2012 20:08:49 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Current GRO can hold packets in gro_list for almost unlimited
> time, in case napi->poll() handler consumes its budget over and over.
> 
> In this case, napi_complete()/napi_gro_flush() are not called.
> 
> Another problem is that gro_list is flushed in non friendly way :
> We scan the list and complete packets in the reverse order.
> (youngest packets first, oldest packets last)
> This defeats priorities that sender could have cooked.
> 
> Since GRO currently only store TCP packets, we dont really notice the
> bug because of retransmits, but this behavior can add unexpected
> latencies, particularly on mice flows clamped by elephant flows.
> 
> This patch makes sure no packet can stay more than 1 ms in queue, and
> only in stress situations.
> 
> It also complete packets in the right order to minimize latencies.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.
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