netdev - Re: [PATCH net-next] tcp: add a force_schedule argument to sk_stream_alloc

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Message-Id: <20150521.165813.1925516530964458536.davem@davemloft.net>
Date:	Thu, 21 May 2015 16:58:13 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: add a force_schedule argument to
 sk_stream_alloc_skb()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 19 May 2015 13:26:55 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> In commit 8e4d980ac215 ("tcp: fix behavior for epoll edge trigger")
> we fixed a possible hang of TCP sockets under memory pressure,
> by allowing sk_stream_alloc_skb() to use sk_forced_mem_schedule()
> if no packet is in socket write queue.
> 
> It turns out there are other cases where we want to force memory
> schedule :
> 
> tcp_fragment() & tso_fragment() need to split a big TSO packet into
> two smaller ones. If we block here because of TCP memory pressure,
> we can effectively block TCP socket from sending new data.
> If no further ACK is coming, this hang would be definitive, and socket
> has no chance to effectively reduce its memory usage.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Looks good, applied, thanks Eric.
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