netdev - Re: [PATCH v2 net-next] tcp: fix slow start after idle vs TSO/GSO

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Message-Id: <20150825.112319.941840654581719226.davem@davemloft.net>
Date:	Tue, 25 Aug 2015 11:23:19 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com
Subject: Re: [PATCH v2 net-next] tcp: fix slow start after idle vs TSO/GSO

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 21 Aug 2015 12:30:00 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> slow start after idle might reduce cwnd, but we perform this
> after first packet was cooked and sent.
> 
> With TSO/GSO, it means that we might send a full TSO packet
> even if cwnd should have been reduced to IW10.
> 
> Moving the SSAI check in skb_entail() makes sense, because
> we slightly reduce number of times this check is done,
> especially for large send() and TCP Small queue callbacks from
> softirq context.
> 
> As Neal pointed out, we also need to perform the check
> if/when receive window opens.
> 
> Tested:
> 
> Following packetdrill test demonstrates the problem
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.
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