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From: Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
To: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>,
	kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org,
	David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
	devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org
Subject: Re: [PATCH v2 3/5] change number_of_cpusets to an atomic
Date: Tue, 24 Apr 2012 11:24:14 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.00.1204241120130.26005@router.home> (raw)
In-Reply-To: <4F96D1A8.6040604-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>

On Tue, 24 Apr 2012, Glauber Costa wrote:

> > Would this not also be a good case to introduce static branching?
> >
> > number_of_cpusets is used to avoid going through unnecessary processing
> > should there be no cpusets in use.
>
> static branches comes with a set of problems themselves, so I usually prefer
> to use them only in places where we don't want to pay even a cache miss if we
> can avoid, or a function call, or anything like that - like the slub cache
> alloc as you may have seen in my kmem memcg series.
>
> It doesn't seem to be the case here.

How did you figure that? number_of_cpusets was introduced exactly because
the functions are used in places where we do not pay the cost of calling
__cpuset_node_allowed_soft/hardwall. Have a look at these. They may take
locks etc etc in critical allocation paths

  parent reply	other threads:[~2012-04-24 16:24 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-23 19:37 [PATCH v2 0/5] Fix problem with static_key decrement Glauber Costa
2012-04-23 19:37 ` Glauber Costa
     [not found] ` <1335209867-1831-1-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-23 19:37   ` [PATCH v2 1/5] don't attach a task to a dead cgroup Glauber Costa
2012-04-23 19:37     ` Glauber Costa
     [not found]     ` <1335209867-1831-2-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24  2:20       ` KAMEZAWA Hiroyuki
2012-04-23 19:37   ` [PATCH v2 2/5] blkcg: protect blkcg->policy_list Glauber Costa
2012-04-23 19:37     ` Glauber Costa
2012-04-23 19:37   ` [PATCH v2 3/5] change number_of_cpusets to an atomic Glauber Costa
2012-04-23 19:37     ` Glauber Costa
     [not found]     ` <1335209867-1831-4-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24  2:25       ` KAMEZAWA Hiroyuki
2012-04-24 15:02     ` Christoph Lameter
     [not found]       ` <alpine.DEB.2.00.1204241001050.26005-sBS69tsa9Uj/9pzu0YdTqQ@public.gmane.org>
2012-04-24 16:15         ` Glauber Costa
2012-04-24 16:15           ` Glauber Costa
     [not found]           ` <4F96D1A8.6040604-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24 16:24             ` Christoph Lameter [this message]
     [not found]               ` <alpine.DEB.2.00.1204241120130.26005-sBS69tsa9Uj/9pzu0YdTqQ@public.gmane.org>
2012-04-24 16:30                 ` Glauber Costa
2012-04-24 16:30                   ` Glauber Costa
     [not found]                   ` <4F96D50D.4020804-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24 18:27                     ` Christoph Lameter
2012-04-23 19:37   ` [PATCH v2 4/5] don't take cgroup_mutex in destroy() Glauber Costa
2012-04-23 19:37     ` Glauber Costa
     [not found]     ` <1335209867-1831-5-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24  2:31       ` KAMEZAWA Hiroyuki
     [not found]         ` <4F96109A.8000907-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2012-04-24 11:42           ` Glauber Costa
2012-04-24 11:42             ` Glauber Costa
     [not found]             ` <4F9691A8.1070106-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-25  8:01               ` Li Zefan
2012-04-23 19:37   ` [PATCH v2 5/5] decrement static keys on real destroy time Glauber Costa
2012-04-23 19:37     ` Glauber Costa
     [not found]     ` <1335209867-1831-6-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-04-24  2:40       ` KAMEZAWA Hiroyuki
     [not found]         ` <4F9612B9.7050705-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
2012-04-24 11:41           ` Glauber Costa
2012-04-24 11:41             ` Glauber Costa
2012-04-25  0:22             ` KAMEZAWA Hiroyuki

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