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From: Andrew Morton <akpm@linux-foundation.org>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Tejun Heo <tj@kernel.org>,
	avi@redhat.com, nate@cpanel.net, cl@linux-foundation.org,
	oleg@redhat.com, axboe@kernel.dk, linux-kernel@vger.kernel.org
Subject: Re: [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock
Date: Tue, 27 Dec 2011 13:25:01 -0800	[thread overview]
Message-ID: <20111227132501.ad7f895f.akpm@linux-foundation.org> (raw)
In-Reply-To: <20111223145856.GB16818@redhat.com>

On Fri, 23 Dec 2011 09:58:56 -0500
Vivek Goyal <vgoyal@redhat.com> wrote:

> > Why do the allocation during I/O?  Can't it be done in the hotplug handler?
> > 
> 
> Even if we can do it in hotplug handler it will be very wasteful of
> memory. So if there are 100 IO cgroups in the system, upon every block
> device hotplug, we will allocate per cpu memory for all the 100 cgroups,
> irrespective of the fact whether they are doing IO to the device or not.
> 
> Now expand this to a system with 100 cgroups and 100 Luns. 10000
> allocations for no reason. (Even if we do it for cgroups needing stats,
> does not help much). Current scheme allocates memory for the group
> only if a sepcific cgroup is doing IO to a specific block device. 

umm, we've already declared that it is OK to completely waste this
memory for the users (probably a majority) who will not be using
these stats.

Also, has this stuff been tested at that scale?  I fear to think what
10000 allocations will do to fragmetnation of the vmalloc() arena.


  reply	other threads:[~2011-12-27 21:25 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-22 21:45 [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock Tejun Heo
2011-12-22 21:45 ` [PATCH 1/7] mempool: fix and document synchronization and memory barrier usage Tejun Heo
2011-12-22 21:45 ` [PATCH 2/7] mempool: drop unnecessary and incorrect BUG_ON() from mempool_destroy() Tejun Heo
2011-12-22 21:45 ` [PATCH 3/7] mempool: fix first round failure behavior Tejun Heo
2011-12-22 21:45 ` [PATCH 4/7] mempool: factor out mempool_fill() Tejun Heo
2011-12-22 21:45 ` [PATCH 5/7] mempool: separate out __mempool_create() Tejun Heo
2011-12-22 21:45 ` [PATCH 6/7] mempool, percpu: implement percpu mempool Tejun Heo
2011-12-22 21:45 ` [PATCH 7/7] block: fix deadlock through percpu allocation in blk-cgroup Tejun Heo
2011-12-23  1:00   ` Vivek Goyal
2011-12-23 22:54     ` Tejun Heo
2011-12-22 21:59 ` [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock Andrew Morton
2011-12-22 22:09   ` Tejun Heo
2011-12-22 22:20     ` Andrew Morton
2011-12-22 22:41       ` Tejun Heo
2011-12-22 22:54         ` Andrew Morton
2011-12-22 23:00           ` Tejun Heo
2011-12-22 23:16             ` Andrew Morton
2011-12-22 23:24               ` Tejun Heo
2011-12-22 23:41                 ` Andrew Morton
2011-12-22 23:54                   ` Tejun Heo
2011-12-23  1:14                     ` Andrew Morton
2011-12-23 15:17                       ` Vivek Goyal
2011-12-27 18:34                       ` Tejun Heo
2011-12-27 21:20                         ` Andrew Morton
2011-12-27 21:44                           ` Tejun Heo
2011-12-27 21:58                             ` Andrew Morton
2011-12-27 22:22                               ` Tejun Heo
2011-12-23  1:21                   ` Vivek Goyal
2011-12-23  1:38                     ` Andrew Morton
2011-12-23  2:54                       ` Vivek Goyal
2011-12-23  3:11                         ` Andrew Morton
2011-12-23 14:58                           ` Vivek Goyal
2011-12-27 21:25                             ` Andrew Morton [this message]
2011-12-27 22:07                               ` Tejun Heo
2011-12-27 22:21                                 ` Andrew Morton
2011-12-27 22:30                                   ` Tejun Heo
2012-01-16 15:26                                     ` Vivek Goyal
2011-12-23  1:40       ` Vivek Goyal
2011-12-23  1:58         ` Andrew Morton
2011-12-23  2:56           ` Vivek Goyal
2011-12-26  6:05             ` KAMEZAWA Hiroyuki
2011-12-27 17:52               ` Tejun Heo
2011-12-28  0:14                 ` KAMEZAWA Hiroyuki
2011-12-28  0:41                   ` Tejun Heo
2012-01-05  1:28                     ` Tejun Heo
2012-01-16 15:28                       ` Vivek Goyal
2012-02-09 23:58                       ` Tejun Heo
2012-02-10 16:26                         ` Vivek Goyal
2012-02-13 22:31                           ` Tejun Heo
2012-02-15 15:43                             ` Vivek Goyal
2011-12-23 14:46           ` Vivek Goyal

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