linux-kernel - Re: [PATCH 11/11] cgroup: use percpu refcnt for cgroup_subsys

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Date:	Fri, 14 Jun 2013 22:39:12 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	lizefan@...wei.com, containers@...ts.linux-foundation.org,
	cgroups@...r.kernel.org, koverstreet@...gle.com,
	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	Mike Snitzer <snitzer@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"Alasdair G. Kergon" <agk@...hat.com>,
	Jens Axboe <axboe@...nel.dk>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Glauber Costa <glommer@...il.com>
Subject: Re: [PATCH 11/11] cgroup: use percpu refcnt for cgroup_subsys_states

On Fri, Jun 14, 2013 at 10:35:22PM -0700, Tejun Heo wrote:
> On Fri, Jun 14, 2013 at 03:31:25PM -0700, Tejun Heo wrote:
> > I'll play with it a bit more on an actual machine and post more
> > results.  Test program attached.
> 
> So, here are the results from the same test on a dual-socket 2-way
> NUMA opteron 8 core machine.
> 
> Running on one CPU.
> 
>   copy size	atomic		percpu		diff in pct
>   0		535964443	616756827	+15.07%
>   32		399988186	378678713	 -5.33%
>   64		389067476	355073979	 -8.74%
>   128		342192631	315615300	 -7.77%
>   256		281208005	260598931	 -7.33%
>   512		188070912	193225269	 +2.74%
> 
> Running on all eight cores.
> 
>   copy size	atomic		percpu		diff in pct
>   0		121324328	4889425511	+3,930.05%
>   32		 96170193	2999613380	+3,019.07%
>   64		 98139061	2813894184	+2,767.25%
>   128		112610025	2503229487	+2,122.92%
>   256		 96828114	2069865752	+2,037.67%
>   512		 95858297	1537726109	+1,504.17%

A bit of addition, this of course is completely synthetic and
exaggerates the differences both ways, but it's pretty clear that this
is gonna be a clear gain in any kind of workload which would generate
some amount of cross-CPU refcnting, which would be the norm anyway.

Thanks.

-- 
tejun
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