netdev - Re: [PATCH v2 net-next] tcp: set SOCK

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Date:	Fri, 15 May 2015 10:20:38 -0400
From:	Jason Baron <jbaron@...mai.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next] tcp: set SOCK_NOSPACE under memory pressure

On 05/14/2015 11:07 PM, Eric Dumazet wrote:
> On Sat, 2015-05-09 at 17:38 -0400, David Miller wrote:
>> Applied, thanks a lot for adding so much information to the commit
>> message.
>> --
> When doing more tests with this stuff, I found we could still have
> hangs, because a TCP socket can end up having no skb in its write queue.
>
> We need to allow one skb (this can be 2KB) to keep the logic being ACK
> driven.
>

Indeed. I alluded to that in the commit message.

The 2KB minimum wouldn't help in the case where we really got
-ENOMEM from the core allocator, unless I guess we reserved
the 2KB permanently. Or we could just issue the wakeup in the
case where we return -EAGAIN and the write queue is empty.
That is a very simple additional change here, I think.

Thanks,

-Jason
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