Re: [patch 0/6] mm: memcg: statistics implementation cleanups
From: Johannes Weiner
Date: Tue May 15 2012 - 07:03:56 EST
On Tue, May 15, 2012 at 09:19:33AM +0900, KAMEZAWA Hiroyuki wrote:
> (2012/05/15 3:00), Johannes Weiner wrote:
> > Before piling more things (reclaim stats) on top of the current mess,
> > I thought it'd be better to clean up a bit.
> > The biggest change is printing statistics directly from live counters,
> > it has always been annoying to declare a new counter in two separate
> > enums and corresponding name string arrays. After this series we are
> > down to one of each.
> > mm/memcontrol.c | 223 +++++++++++++++++------------------------------
> > 1 file changed, 82 insertions(+), 141 deletions(-)
> to all 1-6. Thank you.
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> One excuse for my old implementation of mem_cgroup_get_total_stat(),
> which is fixed in patch 6, is that I thought it's better to touch all counters
> in a cachineline at once and avoiding long distance for-each loop.
> What number of performance difference with some big hierarchy(100+children) tree ?
> (But I agree your code is cleaner. I'm just curious.)
I set up a parental group with hierarchy enabled, then created 512
children and did a 4-job kernel bench in one of them. Every 0.1
seconds, I read the stats of the parent, which requires reading each
stat/event/lru item from 512 groups before moving to the next one:
Walltime (s) 62.61 ( +0.00%) 62.88 ( +0.43%)
Walltime (stddev) 0.17 ( +0.00%) 0.14 ( -3.17%)
That should be acceptable, I think.
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