Re: [PATCH 3/7] drm/i915: Keep a count of requests submitted from userspace

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Tvrtko Ursulin (2018-04-09 11:40:08)
> 
> On 09/04/2018 11:27, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-04-09 11:17:04)
> >>
> >> On 09/04/2018 10:25, Chris Wilson wrote:
> >>> Downside being that we either then use atomic64 throughout or we mix
> >>> atomic32/atomic64 knowing that we're on x86. (I feel like someone else
> >>> must have solved this problem in a much neater way, before they went to
> >>> per-cpu stats ;)
> >>
> >> Is the winky implying you know who and where? :) We have three potential
> >> solutions now, even for if the winky is suggesting something.
> > 
> > Nah, just that atomic/locked counters are so old hat. Not sure if there
> > remain any good examples for hotpath counters that remain applicable to
> > our code.
> 
> Leave it as is then for now and improve if we discover it is not good 
> enough?

I did have an ulterior motive in that the cmpxchg did resolve one issue
that irked me with the two counters being updated out of sync. Minor,
minor glitches :)

I don't have a strong preference either way. These instructions on the
submit are not likely to stand out, as compared to the biggest fish of
ksoftirqd, execlists_schedule() and execlists_dequeue().
-Chris
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