On 07/16/2015 08:59 AM, Tejun Heo wrote:
On Thu, Jul 16, 2015 at 08:48:41AM -0600, Jens Axboe wrote:
I've played with this before, but always ran into the hurdle of making
part_in_flight() too expensive ended up hurting results in the end. Making
the inc/dec parts of accounting percpu is a no-brainer, unfortunately the
summing then becomes pretty expensive. I'll run this through some testing
and see what kind of results I get.
The only place which could be a problem is part_round_stats() and we
can do that *way* lazier. I don't think we're using that internally.
Why are we even invoking it from IO issue / completion path?
Right, that's where it's called in the fast path. Right now, it's
per-jiffy lazy. As to how/when it's called, I don't believe that has
changed since those stats were introduced. If we can move that out of
the fast path, then the percpu changes are straight forward.
--
Jens Axboe
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