linux-kernel - Re: [PATCH v9 15/15] drm/i915: Add deadline based boost support

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Date:   Fri, 3 Mar 2023 13:20:38 -0500
From:   Matt Turner <mattst88@...il.com>
To:     Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
Cc:     Rob Clark <robdclark@...il.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        Daniel Vetter <daniel@...ll.ch>,
        Christian König <ckoenig.leichtzumerken@...il.com>,
        Michel Dänzer <michel@...nzer.net>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Alex Deucher <alexander.deucher@....com>,
        Pekka Paalanen <ppaalanen@...il.com>,
        Simon Ser <contact@...rsion.fr>,
        Luben Tuikov <luben.tuikov@....com>,
        Rob Clark <robdclark@...omium.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        intel-gfx@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH v9 15/15] drm/i915: Add deadline based boost support

On Fri, Mar 3, 2023 at 10:08 AM Tvrtko Ursulin
<tvrtko.ursulin@...ux.intel.com> wrote:
>
>
> On 03/03/2023 14:48, Rob Clark wrote:
> > On Fri, Mar 3, 2023 at 1:58 AM Tvrtko Ursulin
> > <tvrtko.ursulin@...ux.intel.com> wrote:
> >>
> >>
> >> On 03/03/2023 03:21, Rodrigo Vivi wrote:
> >>> On Thu, Mar 02, 2023 at 03:53:37PM -0800, Rob Clark wrote:
> >>>> From: Rob Clark <robdclark@...omium.org>
> >>>>
> >>>
> >>> missing some wording here...
> >>>
> >>>> v2: rebase
> >>>>
> >>>> Signed-off-by: Rob Clark <robdclark@...omium.org>
> >>>> ---
> >>>>    drivers/gpu/drm/i915/i915_request.c | 20 ++++++++++++++++++++
> >>>>    1 file changed, 20 insertions(+)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> >>>> index 7503dcb9043b..44491e7e214c 100644
> >>>> --- a/drivers/gpu/drm/i915/i915_request.c
> >>>> +++ b/drivers/gpu/drm/i915/i915_request.c
> >>>> @@ -97,6 +97,25 @@ static bool i915_fence_enable_signaling(struct dma_fence *fence)
> >>>>       return i915_request_enable_breadcrumb(to_request(fence));
> >>>>    }
> >>>>
> >>>> +static void i915_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> >>>> +{
> >>>> +    struct i915_request *rq = to_request(fence);
> >>>> +
> >>>> +    if (i915_request_completed(rq))
> >>>> +            return;
> >>>> +
> >>>> +    if (i915_request_started(rq))
> >>>> +            return;
> >>>
> >>> why do we skip the boost if already started?
> >>> don't we want to boost the freq anyway?
> >>
> >> I'd wager Rob is just copying the current i915 wait boost logic.
> >
> > Yup, and probably incorrectly.. Matt reported fewer boosts/sec
> > compared to your RFC, this could be the bug
>
> Hm, there I have preserved this same !i915_request_started logic.
>
> Presumably it's not just fewer boosts but lower performance. How is he
> setting the deadline? Somehow from clFlush or so?
>
> Regards,
>
> Tvrtko
>
> P.S. Take note that I did not post the latest version of my RFC. The one
> where I fix the fence chain and array misses you pointed out. I did not
> think it would be worthwhile given no universal love for it, but if
> people are testing with it more widely that I was aware perhaps I should.

Yep, that would be great. We're interested in it for ChromeOS. Please
Cc me on the series when you send it.