Re: [PATCH RFC] time: drop do_sys_times spinlock

[Peter Zijlstra]

On Wed, Aug 13, 2014 at 08:59:50AM +0200, Mike Galbraith wrote:
 
> I was told that clock_gettime(CLOCK_PROCESS_CPUTIME_ID) has scalability
> issues on BIG boxen

> I'm sure the real clock_gettime() using proggy that gummed up a ~1200
> core box for "a while" wasn't the testcase below, which will gum it up
> for a long while, but looks to me like using CLOCK_PROCESS_CPUTIME_ID
> from LOTS of threads is a "Don't do that, it'll hurt a LOT".

Yes, don't do that. Its unavoidably slow and bad.

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