linux-kernel - Re: [PATCH v7 4/8] sched: nominate preferred wakeup cpu

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Date:	Fri, 19 Dec 2008 23:54:54 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	yinghai@...nel.org, svaidy@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, suresh.b.siddha@...el.com,
	venkatesh.pallipadi@...el.com, a.p.zijlstra@...llo.nl,
	dipankar@...ibm.com, balbir@...ux.vnet.ibm.com,
	vatsa@...ux.vnet.ibm.com, ego@...ibm.com, andi@...stfloor.org,
	davecb@....com, tconnors@...ro.swin.edu.au, maxk@...lcomm.com,
	gregory.haskins@...il.com, pavel@...e.cz, rusty@...tcorp.com.au
Subject: Re: [PATCH v7 4/8] sched: nominate preferred wakeup cpu


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 19 Dec 2008 23:31:30 +0100
> Ingo Molnar <mingo@...e.hu> wrote:
> 
> > * Ingo Molnar <mingo@...e.hu> wrote:
> > 
> > > > [   74.013893]  <EOI> <0>Code: 8b 47 08 4a 8b 0c 00 48 85 c9 0f 84 c3 00 00 00 49 8b 47 10 4a 8b 04 00 48 8b 80 a8 00 00 00 48 85 c0 74 13 48 0f af 45 c8 31 d2 <48> f7 75 c0 49 89 c6 48 89 c6 eb 16 48 63 55 d0 48 8b 45 c8 45 
> > > > [   74.013893] RIP  [<ffffffff802375d8>] tg_shares_up+0x113/0x1f1
> > > > [   74.013893]  RSP <ffff88025e057d88>
> > > > [   74.020022] ---[ end trace 2fc4046e394f2312 ]---
> > > > [   74.020188] Kernel panic - not syncing: Fatal exception in interrupt
> > > > 
> > > > config: http://userweb.kernel.org/~akpm/config-akpm2.txt
> > > > 
> > > > I'll try hacking some div-by-zero avoidance into update_group_shares_cpu().
> > > 
> > > hm, weird - Yinghai noticed this crash in -tip and we have that patch 
> > > zapped from all -*-next branches already.
> > 
> > I guess you applied Ken's patch from email and had it in -mm?
> 
> Nope.
> 
> > We have a 
> > new version of that patch from Ken now based on Yinghai's bugreport - only 
> > lightly tested for now.
> > 
> > 	Ingo
> > 
> > ----------->
> > >From d71f5a7c8bf9cd7c74159a53e522e363f2eddaf5 Mon Sep 17 00:00:00 2001
> > From: Ken Chen <kenchen@...gle.com>
> > Date: Fri, 19 Dec 2008 10:11:50 -0800
> > Subject: [PATCH] sched: fix uneven per-cpu task_group share distribution
> 
> linux-next has:
> 
> commit 6eed5aaacae0ced9a43a923633befd2c695d6620
> Author: Ken Chen <kenchen@...gle.com>
> Date:   Mon Dec 15 23:37:50 2008 -0800
> 
>     sched: fix uneven per-cpu task_group share distribution
> 
> so I guess we have a latency problem.

ah, yes. I did this 22 hours ago:

| commit ea52f4ea5666ffed175ec41efac52b560818563d
| Author: Ingo Molnar <mingo@...e.hu>
| Date:   Fri Dec 19 02:09:20 2008 +0100
|
|     Revert "sched: fix uneven per-cpu task_group share distribution"
|    
|     This reverts commit 6eed5aaacae0ced9a43a923633befd2c695d6620.
|    
|     Causes crashes.

So should be fixed in the next linux-next iteration.

	Ingo
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