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From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	John.C.Harrison@Intel.com, Intel-GFX@Lists.FreeDesktop.Org,
	"Lankhorst, Maarten" <maarten.lankhorst@intel.com>,
	"Syrjala, Ville" <ville.syrjala@intel.com>
Subject: Re: [PATCH v5 09/35] drm/i915: Force MMIO flips when scheduler enabled
Date: Mon, 22 Feb 2016 12:42:48 -0800	[thread overview]
Message-ID: <56CB72C8.1030505@virtuousgeek.org> (raw)
In-Reply-To: <20160220092214.GQ28380@nuc-i3427.alporthouse.com>

On 02/20/2016 01:22 AM, Chris Wilson wrote:
> On Fri, Feb 19, 2016 at 11:28:05AM -0800, Jesse Barnes wrote:
>> On 02/18/2016 06:26 AM, John.C.Harrison@Intel.com wrote:
>>> From: John Harrison <John.C.Harrison@Intel.com>
>>>
>>> MMIO flips are the preferred mechanism now
> 
> Because introducing variable latency in waking up a big core is a good
> idea?

Is the latency variability really that bad?  I'm not too concerned about waking up the core either, I think it's going to be hit up quite a bit in these situations anyway, and vblanks should be driving the rendering as well.

>> but more importantly, pipe
>>> based flips cause issues for the scheduler. Specifically, submitting
>>> work to the rings around the side of the scheduler could cause that
>>> work to be lost if the scheduler generates a pre-emption event on that
>>> ring.
> 
> No. That is just incredibily bad design.
> 
>> Why can't we use mmio flips unconditionally?  Maarten or Ville?
> 
> Why would we want to? CS flips work just fine in execlists and no reason
> was ever given as to why they were not enabled, just laziness.

I'm not saying it can't be done, but I thought with atomic we decided to go with mmio because it makes things a lot simpler (iirc Ville's design did that way back?).

I'm fine with either, but it seems like we should settle on one rather than trying to maintain two different ways of flipping.  We'll have work to do either way.

Jesse

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  reply	other threads:[~2016-02-22 20:43 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-18 14:26 [PATCH v5 00/35] GPU scheduler for i915 driver John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 01/35] drm/i915: Add total count to context status debugfs output John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 02/35] drm/i915: Prelude to splitting i915_gem_do_execbuffer in two John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 03/35] drm/i915: Split i915_dem_do_execbuffer() in half John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 04/35] drm/i915: Cache request pointer in *_submission_final() John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 05/35] drm/i915: Re-instate request->uniq because it is extremely useful John.C.Harrison
2016-02-18 14:26 ` [PATCH v5 06/35] drm/i915: Start of GPU scheduler John.C.Harrison
2016-02-19 13:03   ` Joonas Lahtinen
2016-02-19 17:03     ` John Harrison
2016-02-26  9:13       ` Joonas Lahtinen
2016-02-26 14:18         ` John Harrison
2016-02-18 14:26 ` [PATCH v5 07/35] drm/i915: Prepare retire_requests to handle out-of-order seqnos John.C.Harrison
2016-02-19 19:23   ` Jesse Barnes
2016-02-18 14:26 ` [PATCH v5 08/35] drm/i915: Disable hardware semaphores when GPU scheduler is enabled John.C.Harrison
2016-02-19 19:27   ` Jesse Barnes
2016-02-18 14:26 ` [PATCH v5 09/35] drm/i915: Force MMIO flips when scheduler enabled John.C.Harrison
2016-02-19 19:28   ` Jesse Barnes
2016-02-19 19:53     ` Ville Syrjälä
2016-02-19 20:01       ` Jesse Barnes
2016-02-22  9:41         ` Lankhorst, Maarten
2016-02-22 12:53           ` John Harrison
2016-02-20  9:22     ` Chris Wilson
2016-02-22 20:42       ` Jesse Barnes [this message]
2016-02-23 11:16         ` Chris Wilson
2016-02-18 14:26 ` [PATCH v5 10/35] drm/i915: Added scheduler hook when closing DRM file handles John.C.Harrison
2016-03-01  8:59   ` Joonas Lahtinen
2016-03-01 14:52     ` John Harrison
2016-02-18 14:26 ` [PATCH v5 11/35] drm/i915: Added scheduler hook into i915_gem_request_notify() John.C.Harrison
2016-03-01  9:10   ` Joonas Lahtinen
2016-02-18 14:27 ` [PATCH v5 12/35] drm/i915: Added deferred work handler for scheduler John.C.Harrison
2016-03-01  9:16   ` Joonas Lahtinen
2016-03-01 15:12     ` John Harrison
2016-02-18 14:27 ` [PATCH v5 13/35] drm/i915: Redirect execbuffer_final() via scheduler John.C.Harrison
2016-02-19 19:33   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 14/35] drm/i915: Keep the reserved space mechanism happy John.C.Harrison
2016-02-19 19:36   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 15/35] drm/i915: Added tracking/locking of batch buffer objects John.C.Harrison
2016-02-19 19:42   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 16/35] drm/i915: Hook scheduler node clean up into retire requests John.C.Harrison
2016-02-19 19:44   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 17/35] drm/i915: Added scheduler support to __wait_request() calls John.C.Harrison
2016-03-01 10:02   ` Joonas Lahtinen
2016-03-11 11:47     ` John Harrison
2016-02-18 14:27 ` [PATCH v5 18/35] drm/i915: Added scheduler support to page fault handler John.C.Harrison
2016-02-19 19:45   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 19/35] drm/i915: Added scheduler flush calls to ring throttle and idle functions John.C.Harrison
2016-03-07 11:31   ` Joonas Lahtinen
2016-03-11 16:22     ` John Harrison
2016-02-18 14:27 ` [PATCH v5 20/35] drm/i915: Add scheduler hook to GPU reset John.C.Harrison
2016-02-23 20:27   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 21/35] drm/i915: Added a module parameter to allow the scheduler to be disabled John.C.Harrison
2016-02-23 20:29   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 22/35] drm/i915: Support for 'unflushed' ring idle John.C.Harrison
2016-02-23 20:35   ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 23/35] drm/i915: Defer seqno allocation until actual hardware submission time John.C.Harrison
2016-03-07 12:16   ` Joonas Lahtinen
2016-02-18 14:27 ` [PATCH v5 24/35] drm/i915: Added trace points to scheduler John.C.Harrison
2016-02-23 20:42   ` Jesse Barnes
2016-02-23 20:42   ` Jesse Barnes
2016-02-26 15:55     ` John Harrison
2016-02-26 17:12       ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 25/35] drm/i915: Added scheduler queue throttling by DRM file handle John.C.Harrison
2016-02-23 21:02   ` Jesse Barnes
2016-03-01 15:52     ` John Harrison
2016-02-18 14:27 ` [PATCH v5 26/35] drm/i915: Added debugfs interface to scheduler tuning parameters John.C.Harrison
2016-02-23 21:06   ` Jesse Barnes
2016-03-11 16:28     ` John Harrison
2016-03-11 17:25       ` Jesse Barnes
2016-02-18 14:27 ` [PATCH v5 27/35] drm/i915: Added debug state dump facilities to scheduler John.C.Harrison
2016-03-07 12:31   ` Joonas Lahtinen
2016-03-11 16:38     ` John Harrison
2016-03-15 10:53       ` Joonas Lahtinen
2016-02-18 14:27 ` [PATCH v5 28/35] drm/i915: Add early exit to execbuff_final() if insufficient ring space John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 29/35] drm/i915: Added scheduler statistic reporting to debugfs John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 30/35] drm/i915: Add scheduler support functions for TDR John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 31/35] drm/i915: Scheduler state dump via debugfs John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 32/35] drm/i915: Enable GPU scheduler by default John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 33/35] drm/i915: Add scheduling priority to per-context parameters John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 34/35] drm/i915: Add support for retro-actively banning batch buffers John.C.Harrison
2016-02-18 14:27 ` [PATCH v5 35/35] drm/i915: Allow scheduler to manage inter-ring object synchronisation John.C.Harrison
2016-02-18 14:27 ` [PATCH 01/20] igt/gem_ctx_param_basic: Updated to support scheduler priority interface John.C.Harrison
2016-02-18 15:30 ` ✗ Fi.CI.BAT: failure for GPU scheduler for i915 driver Patchwork

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