Re: [PATCH v3] drm/i915: Optimistically spin for the request completion

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH v3] drm/i915: Optimistically spin for the request completion
Date: Thu, 12 Mar 2015 13:14:30 +0000	[thread overview]
Message-ID: <55019136.4@linux.intel.com> (raw)
In-Reply-To: <1426158677-26261-1-git-send-email-chris@chris-wilson.co.uk>

On 03/12/2015 11:11 AM, Chris Wilson wrote:
> This provides a nice boost to mesa in swap bound scenarios (as mesa
> throttles itself to the previous frame and given the scenario that will
> complete shortly). It will also provide a good boost to systems running
> with semaphores disabled and so frequently waiting on the GPU as it
> switches rings. In the most favourable of microbenchmarks, this can
> increase performance by around 15% - though in practice improvements
> will be marginal and rarely noticeable.
>
> v2: Account for user timeouts
> v3: Limit the spinning to a single jiffie (~1us) at most. On an
> otherwise idle system, there is no scheduler contention and so without a
> limit we would spin until the GPU is ready.

Isn't one jiffie 1-10ms typically?

Regards,

Tvrtko

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