From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: commit e9e9250b: sync wakeup bustage when waker is an RT task
Date: Mon, 31 May 2010 15:56:49 +0200 [thread overview]
Message-ID: <1275314209.17599.7.camel@marge.simson.net> (raw)
In-Reply-To: <1275306978.27810.22357.camel@twins>
On Mon, 2010-05-31 at 13:56 +0200, Peter Zijlstra wrote:
> On Sun, 2010-05-16 at 09:21 +0200, Mike Galbraith wrote:
> > sched: RT waker sync wakeup bugfix
> >
> > An RT waker's weight is not on the runqueue, but we try to subrtact it anyway
> > in the sync wakeup case, sending this_load negative. This leads to affine
> > wakeup failure in cases where it should succeed. This was found while testing
> > an PREEMPT_RT kernel with lmbench's lat_udp. In a PREEMPT_RT kernel, softirq
> > threads act as a ~proxy for the !RT buddy. Approximate !PREEMPT_RT sync wakeup
> > behavior by looking at the buddy instead, and subtracting the maximum task weight
> > that will not send this_load negative.
>
>
> Does the below work?
Had to make a dinky adjustment for x86-tip-rt33, but yeah, the horrid
latencies are gone. (hm, skinnier than expected too)
-Mike
next prev parent reply other threads:[~2010-05-31 13:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-15 11:57 commit e9e9250b: sync wakeup bustage when waker is an RT task Mike Galbraith
2010-05-15 12:04 ` Peter Zijlstra
2010-05-15 17:07 ` Mike Galbraith
2010-05-15 17:32 ` Mike Galbraith
2010-05-16 7:21 ` Mike Galbraith
2010-05-17 4:38 ` Mike Galbraith
2010-05-17 8:49 ` Peter Zijlstra
2010-05-17 8:52 ` Peter Zijlstra
2010-05-17 9:04 ` Mike Galbraith
2010-05-31 11:56 ` Peter Zijlstra
2010-05-31 13:56 ` Mike Galbraith [this message]
2010-05-31 14:28 ` Peter Zijlstra
2010-05-31 18:03 ` Mike Galbraith
2010-06-01 6:40 ` Mike Galbraith
2010-06-01 9:12 ` [tip:sched/urgent] sched: Fix wake_affine() vs RT tasks tip-bot for Peter Zijlstra
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