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From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Dave Gordon <david.s.gordon@intel.com>, Intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915/guc: Do not use wait_for_atomic in host2guc_action
Date: Tue, 28 Jun 2016 17:04:59 +0100	[thread overview]
Message-ID: <5772A02B.9010604@linux.intel.com> (raw)
In-Reply-To: <57729CD3.8000004@intel.com>


On 28/06/16 16:50, Dave Gordon wrote:
> On 28/06/16 15:30, Tvrtko Ursulin wrote:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> host2guc_action does not appear to be called from atomic context
>> so a more polite wait_for macro should be used. Especially since
>> the timeout is 10ms.
>
> Maybe. However we don't really want to sleep if the action takes only a
> few microseconds, which some of them do. Maybe we need an optimistic
> spin for a few uS to handle the quick commands followed by a sleeping
> wait in the cases where it takes long enough that we don't mind the
> extra wakeup latency?

I believe Mika is working on smart waits similar to what you describe. 
Adaptive back-off etc.

In the meantime how about calling _wait_for directly and setting the 
re-check period to something you think is more appropriate for the GuC?

Shouldn't be less than 10us since usleep_range recommends against it.

Regards,

Tvrtko
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      reply	other threads:[~2016-06-28 16:05 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-28 14:30 [PATCH] drm/i915/guc: Do not use wait_for_atomic in host2guc_action Tvrtko Ursulin
2016-06-28 15:06 ` ✗ Ro.CI.BAT: failure for " Patchwork
2016-06-28 15:50 ` [PATCH] " Dave Gordon
2016-06-28 16:04   ` Tvrtko Ursulin [this message]

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