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From: David Ahern <dsahern@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: deadlock in scheduler enabling HRTICK feature
Date: Thu, 27 Jun 2013 16:28:57 -0600	[thread overview]
Message-ID: <51CCBCA9.1000200@gmail.com> (raw)
In-Reply-To: <20130627104309.GQ28407@twins.programming.kicks-ass.net>

On 6/27/13 4:43 AM, Peter Zijlstra wrote:
> On Wed, Jun 26, 2013 at 10:46:33AM -0600, David Ahern wrote:
>> On 6/26/13 1:05 AM, Peter Zijlstra wrote:
>>>> What is the expectation that the feature provides? not a whole lot of
>>>> documentation on it. I walked down the path wondering if it solved an odd
>>>> problem we are seeing with the CFS in 2.6.27 kernel.
>>>
>>> Its supposed to use hrtimers for slice expiry instead of the regular tick.
>>
>> So theoretically CPU bound tasks would get preempted sooner? That was my
>> guess/hope anyways.
>
> Doth the below worketh?

It doth.

Usually make -j 8 for a kernel build in a VM would lock it up pretty 
quickly. With the patch I was able to run full builds multiple times.

As for the solution you are avoiding the nesting by not waking up the 
softirq daemon.

I'll backport to 2.6.27 and see what happens. Thanks for the patch.

David


  parent reply	other threads:[~2013-06-27 22:29 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-25 21:05 David Ahern
2013-06-25 21:17 ` Peter Zijlstra
2013-06-25 21:20   ` David Ahern
2013-06-26  7:05     ` Peter Zijlstra
2013-06-26 16:46       ` David Ahern
2013-06-27 10:43         ` Peter Zijlstra
2013-06-27 10:53           ` Peter Zijlstra
2013-06-27 12:28             ` Mike Galbraith
2013-06-27 13:06             ` Ingo Molnar
2013-06-27 19:18             ` Andy Lutomirski
2013-06-27 20:37               ` Peter Zijlstra
2013-06-27 22:28           ` David Ahern [this message]
2013-06-28  9:00             ` Ingo Molnar
2013-06-28  9:18               ` Peter Zijlstra
2013-07-12 13:29                 ` [tip:sched/core] sched: Fix HRTICK tip-bot for Peter Zijlstra
2013-06-28  9:09             ` deadlock in scheduler enabling HRTICK feature Peter Zijlstra
2013-06-28 17:28               ` David Ahern

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