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Subject: Re: [PATCH 2/4] coredump: speedup SIGKILL sending
From: Lee Revell <rlrevell@joe-job.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@osdl.org>, "Eric W. Biederman" <ebiederm@xmission.com>,
       Ingo Molnar <mingo@elte.hu>, "Paul E. McKenney" <paulmck@us.ibm.com>,
       Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org
In-Reply-To: <20060406235519.GA331@oleg>
References: <20060406220628.GA237@oleg> <1144352758.2866.105.camel@mindpipe>
	 <20060406235519.GA331@oleg>
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Date: Thu, 06 Apr 2006 16:07:45 -0400
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On Fri, 2006-04-07 at 03:55 +0400, Oleg Nesterov wrote:
> On 04/06, Lee Revell wrote:
> > On Fri, 2006-04-07 at 02:06 +0400, Oleg Nesterov wrote:
> > > With this patch a thread group is killed atomically under ->siglock.
> > > This is faster because we can use sigaddset() instead of force_sig_info()
> > > and this is used in further patches.
> > > 
> > > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
> > 
> > Won't this cause huge latencies when a process with lots of threads is
> > killed?
> 
> Yes, irqs are disabled. But this is not worse than 'kill -9 pid', note
> that __group_complete_signal() or zap_other_threads() do the same.

Those have been problematic in the past.  I am just wondering if this
will be a latency regression, or if changes elsewhere in your patch
negate the effect.

I'm just concerned because it was a lot of work over ~2 years to get 2.6
to perform decently in this area, and we have regressed since 2.6.14 (VM
issue).

Lee