Messages in this thread | | | Date | Wed, 12 Aug 2009 09:26:05 +0530 | From | Balbir Singh <> | Subject | Re: Help Resource Counters Scale better (v4) |
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* Andrew Morton <akpm@linux-foundation.org> [2009-08-11 16:31:59]:
> On Tue, 11 Aug 2009 20:14:05 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > Enhancement: Remove the overhead of root based resource counter accounting > > > > From: Balbir Singh <balbir@linux.vnet.ibm.com> > > > > This patch reduces the resource counter overhead (mostly spinlock) > > associated with the root cgroup. This is a part of the several > > patches to reduce mem cgroup overhead. I had posted other > > approaches earlier (including using percpu counters). Those > > patches will be a natural addition and will be added iteratively > > on top of these. > > > > The patch stops resource counter accounting for the root cgroup. > > The data for display is derived from the statisitcs we maintain > > via mem_cgroup_charge_statistics (which is more scalable). > > > > The tests results I see on a 24 way show that > > > > 1. The lock contention disappears from /proc/lock_stats > > 2. The results of the test are comparable to running with > > cgroup_disable=memory. > > > > Please test/review. > > I don't get it. > > The patch apepars to skip accounting altogether for the root memcgroup > and then adds some accounting back in for swap. Or something like > that. How come? Do we actually not need the root memcgroup > accounting? >
The changelog mentions that the statistics are derived. For memsw as Daisuke-San mentioned, the SWAP accounting is for memsw. We can derive memory.usage_in_bytes from RSS+Cache fields in the memory.stat accounting. For memsw, we needed SWAP accounting.
> IOW, the changelog sucks ;) > > Is this an alternative approach to using percpu_counters, or do we do > both or do we choose one or the other? res_counter_charge() really is > quite sucky. > > The patch didn't have a signoff. > > It would be nice to finalise those performance testing results and > include them in the new, improved patch description. >
I'll submit a new patch with better changelog, checkpatch.pl fixes and test results.
-- Balbir
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