linux-kernel - Re: [PATCH 0/4] cpuset: cleanups and fixes

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Message-Id: <20090226170938.3f5f32a4.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 26 Feb 2009 17:09:38 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] cpuset: cleanups and fixes

On Thu, 26 Feb 2009 15:58:34 +0800
Li Zefan <lizf@...fujitsu.com> wrote:

> KAMEZAWA Hiroyuki wrote:
> > On Thu, 26 Feb 2009 15:02:15 +0800
> > Li Zefan <lizf@...fujitsu.com> wrote:
> > 
> >> This patchset mainly simplifies update_tasks_nodemask() and makes it
> >> return void (won't fail), thus fix a case that writing to cpuset.mems
> >> returns -ENOMEM but its mems_allowed has been changed.
> >>
> >> [PATCH 1/4] cgroups: add 'data' field to struct cgroup_scanner
> >> [PATCH 2/4] cpuset: rewrite update_tasks_nodemask()
> >> [PATCH 3/4] cpuset: avoid changing cpuset's mems when errno returned
> >> [PATCH 4/4] cpuset: remove struct cpuset_hotplug_scanner
> >>
> > Thank you. I think there is no problematic in your patch.
> > 
> > After reading your patch, I wonder we can improve this migration by
> > filter for cgroup_scan_tasks().
> > 
> > Assume a task with tons of threads in a cgroup and
> >   - change nodemask
> >   - migrate=1
> > 
> > Under current implemntation, cpuset_migrate_mm=>do_migrate_mm is called per
> > threads. This implies there will be big overhead, useless scanning of page
> > tables.
> > 
> > Can we add some checks as "Is this mm already migrated ?", anywhere ?
> > (we may need to add some another array, again...)
> > 
> 
> cpuset's memory_migrate flag is disabled by default, and I guess migrating mm
> in cpuset is not frequently used? I tend to not optimise it unless it becomes
> a problem in real-life. :)
> 

Ok, I will do by myself.
-Kame

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