Messages in this thread | | | Date | Tue, 27 Dec 2011 14:21:56 -0800 | From | Andrew Morton <> | Subject | Re: [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock |
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On Tue, 27 Dec 2011 14:07:53 -0800 Tejun Heo <tj@kernel.org> wrote:
> Hello, > > On Tue, Dec 27, 2011 at 01:25:01PM -0800, Andrew Morton wrote: > > 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. > > We're talking about combinatorial combinations where only small subset > is usually expected to be used and, in addition to the absolute usage, > there's big advantage in showing behavior which users would expect. > If 1000 cgroups are doing IOs to 1000 devices, it's expected to > consume some amount of resource.
<autorepeat>For those users who don't want the stats, stats shouldn't consume any resources at all.
And I bet that the majority of the minority who want stats simply want to know "how much IO is this cgroup doing", and don't need per-cgroup, per-device accounting.
And it could be that the minority of the minority who want per-device, per-cgroup stats only want those for a minority of the time.
IOW, what happens if we give 'em atomic_add() and be done with it?
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