Re: [PATCH -tip] cpuacct: Make cpuacct hierarchy walk incpuacct_charge() safe when rcupreempt is used.

[KAMEZAWA Hiroyuki]

On Wed, 18 Mar 2009 10:18:01 +0530
Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx> wrote:
> Looks ok to me, but will wait for experts' comments.
> 
> However, I did a quick measurement of read times with percpu_counter_read()
> (no readside lock) and percpu_counter_sum() (readside lock) and I don't
> see a major slowdown with percpu_counter_sum().
> 
> Time taken for 100 reads of cpuacct.stat with 1s delay b/n every read.
> percpu_counter_read() - 9845 us
> percpu_counter_sum() - 9974 us
> 
Then, almost 1 us overhead per read().....Hmm, seems big (as counter).

Thanks,
-Kame

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