netdev - Re: [PATCH net] tcp/dccp: do not block bh too long in inet_twdr_twkill

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Message-Id: <20150412.230129.1277998183742216856.davem@davemloft.net>
Date:	Sun, 12 Apr 2015 23:01:29 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp/dccp: do not block bh too long in
 inet_twdr_twkill_work()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 12 Apr 2015 18:52:37 -0700

> On Sun, 2015-04-12 at 21:04 -0400, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Fri, 10 Apr 2015 04:19:07 -0700
>> 
>> > From: Eric Dumazet <edumazet@...gle.com>
>> > 
>> > I have seen inet_twdr_twkill_work() blocking softirq for
>> > periods up to 1.5 seconds, depending on number of timewait sockets.
>> > 
>> > This is an unacceptable source of latency.
>> > 
>> > Note that inet_twdr_do_twkill_work() releases death_lock spinlock
>> > for every tw handled, but does not take care of bh enabling.
>> > 
>> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> 
>> I think it makes sense to use local_softirq_pending() here rather
>> than flip the lock unconditionally.
> 
> I thought about that, but this meant having to test 2 conditions.
> 
> Not sure we need this patch anyway, if we merge the 'tcp/dccp: get rid
> of central timewait timer' in 4.1 
> 
> Its not like it is a new bug ...

Yeah, since 4.0 is out already, probably just pass on this patch.
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