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From: Chris Wilson <chris@chris-wilson.co.uk>
To: Mika Kuoppala <mika.kuoppala@linux.intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 04/33] drm/i915/gt: Check for a completed last request once
Date: Thu, 02 Jul 2020 16:53:38 +0100
Message-ID: <159370521882.22925.15420523796843660304@build.alporthouse.com> (raw)
In-Reply-To: <87a70h538x.fsf@gaia.fi.intel.com>

Quoting Mika Kuoppala (2020-07-02 16:46:22)
> Chris Wilson <chris@chris-wilson.co.uk> writes:
> 
> > Pull the repeated check for the last active request being completed to a
> > single spot, when deciding whether or not execlist preemption is
> > required.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_lrc.c | 14 ++++----------
> >  1 file changed, 4 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > index 4eb397b0e14d..7bdbfac26d7b 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > @@ -2137,12 +2137,11 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> >        */
> >  
> >       if ((last = *active)) {
> > -             if (need_preempt(engine, last, rb)) {
> > -                     if (i915_request_completed(last)) {
> > -                             tasklet_hi_schedule(&execlists->tasklet);
> > -                             return;
> > -                     }
> > +             if (i915_request_completed(last) &&
> > +                 !list_is_last(&last->sched.link, &engine->active.requests))
> 
> You return if it is not last? Also the hi schedule is gone.

The kick was just causing us to busyspin ahead of the HW CS event. On
tracing, it did not seem worth it.

If this is the last request, the GPU is now idling and we know that we
will not try and lite restore into that request/context. So instead of
waiting for the CS event, we go ahead and prepare the next pair of
contexts.

If it was not the last request, we know there is a context the GPU will
switch into, so the urgency is not an issue. However, we have to be
careful that we don't issue an ELSP into that second context in case we
catch it as it idles (thus hanging the HW).
-Chris
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  reply index

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-01  8:40 [Intel-gfx] [PATCH 01/33] drm/i915/gt: Harden the heartbeat against a stuck driver Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 02/33] drm/i915/gt: Move the heartbeat into the highprio system wq Chris Wilson
2020-07-02  9:33   ` Mika Kuoppala
2020-07-01  8:40 ` [Intel-gfx] [PATCH 03/33] drm/i915/gt: Decouple completed requests on unwind Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 04/33] drm/i915/gt: Check for a completed last request once Chris Wilson
2020-07-02 15:46   ` Mika Kuoppala
2020-07-02 15:53     ` Chris Wilson [this message]
2020-07-01  8:40 ` [Intel-gfx] [PATCH 05/33] drm/i915/gt: Replace direct submit with direct call to tasklet Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 06/33] drm/i915/gt: Use virtual_engine during execlists_dequeue Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 07/33] drm/i915/gt: Decouple inflight virtual engines Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 08/33] drm/i915/gt: Defer schedule_out until after the next dequeue Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 09/33] drm/i915/gt: Resubmit the virtual engine on schedule-out Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 10/33] drm/i915/gt: Simplify virtual engine handling for execlists_hold() Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 11/33] drm/i915/gt: ce->inflight updates are now serialised Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 12/33] drm/i915/gt: Drop atomic for engine->fw_active tracking Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 13/33] drm/i915/gt: Extract busy-stats for ring-scheduler Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 14/33] drm/i915/gt: Convert stats.active to plain unsigned int Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 15/33] drm/i915: Lift waiter/signaler iterators Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 16/33] drm/i915: Strip out internal priorities Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 17/33] drm/i915: Remove I915_USER_PRIORITY_SHIFT Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 18/33] drm/i915: Replace engine->schedule() with a known request operation Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 19/33] drm/i915/gt: Do not suspend bonded requests if one hangs Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 20/33] drm/i915: Teach the i915_dependency to use a double-lock Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 21/33] drm/i915: Restructure priority inheritance Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 22/33] drm/i915/gt: Remove timeslice suppression Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 23/33] drm/i915: Fair low-latency scheduling Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 24/33] drm/i915/gt: Specify a deadline for the heartbeat Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 25/33] drm/i915: Replace the priority boosting for the display with a deadline Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 26/33] drm/i915: Move saturated workload detection to the GT Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 27/33] Restore "drm/i915: drop engine_pin/unpin_breadcrumbs_irq" Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 28/33] drm/i915/gt: Couple tasklet scheduling for all CS interrupts Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 29/33] drm/i915/gt: Support creation of 'internal' rings Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 30/33] drm/i915/gt: Use client timeline address for seqno writes Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 31/33] drm/i915/gt: Infrastructure for ring scheduling Chris Wilson
2020-07-01 19:42   ` kernel test robot
2020-07-01  8:40 ` [Intel-gfx] [PATCH 32/33] drm/i915/gt: Implement ring scheduler for gen6/7 Chris Wilson
2020-07-01  8:40 ` [Intel-gfx] [PATCH 33/33] drm/i915/gt: Enable ring scheduling " Chris Wilson
2020-07-01  9:37 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [01/33] drm/i915/gt: Harden the heartbeat against a stuck driver Patchwork
2020-07-01  9:38 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2020-07-01  9:58 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-07-01 14:36 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2020-07-02  9:39 ` [Intel-gfx] [PATCH 01/33] " Mika Kuoppala

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