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Date: Thu, 12 Mar 2009 09:14:08 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: balbir@...ux.vnet.ibm.com Cc: bharata@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org, Balaji Rao <balajirrao@...il.com>, Dhaval Giani <dhaval@...ux.vnet.ibm.com>, Li Zefan <lizf@...fujitsu.com>, Paul Menage <menage@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1 On Wed, 11 Mar 2009 21:04:34 +0530 Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: > > > This patch adds a new file cpuacct.stat which displays two stats: > > > utime and stime. I wasn't too sure about the usefulness of providing > > > per-cgroup guest and steal times and hence not including them here. > > > > > > Note that I am using percpu_counter for collecting these two stats. > > > Since percpu_counter subsystem doesn't protect the readside, readers could > > > theoritically obtain incorrect values for these stats on 32bit systems. > > > > Using percpu_counter_read() means that .. but is it okay to ignore "batch" > > number ? (see FBC_BATCH) > > > > FBC_BATCH? Thats gone..no? We have dynamic batches now, IIRC. Could > you please elaborate on your comment? > Ah, ok. it's now extern int percpu_counter_batch. -Kame > > > > > I hope occasional wrong values is not too much of a concern for > > > statistics like this. If it is a problem, we have to either fix > > > percpu_counter or do it all by ourselves as Kamezawa attempted > > > for cpuacct.usage (http://lkml.org/lkml/2009/3/4/14) > > > > > Hmm, percpu_counter_sum() is bad ? > > > > Yes, but we need to sum somewhere.. user space summing will not be > atomic, we'll get several snapshots of per CPU data and summing it > might not yield the correct answers. > > > BTW, I'm not sure but don't we need special handling if > > CONFIG_VIRT_CPU_ACCOUNTING=y ? > > Good point. Bharata, with CONFIG_VIRT_CPU_ACCOUNTING, utime and stime > is accounted for within the architecture. > > -- > Balbir > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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