Re: [cgroup] a0f9ec1f181: -4.3% will-it-scale.per_thread_ops

From: Mike Galbraith
Date: Thu May 15 2014 - 03:11:25 EST


On Thu, 2014-05-15 at 02:14 -0400, Tejun Heo wrote:

> Hmmm... I'm completely stumped. The commit in question has nothing to
> do with tmpfs. It only affects three cgroup files - "tasks",
> "cgroup.procs" and "release_agent". It can't possibly have any effect
> on tmpfs operation. Maybe random effect through code alignment? Even
> that is highly unlikely.

Unlikely, but it happens. I bisected a tbench regression down to a
completely unrelated driver change, and watched it repeatably drop
throughput 5% despite skeptical "No way, show me that trick again".

-Mike

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