From: Matthew Brost <matthew.brost@intel.com>
To: John Harrison <john.c.harrison@intel.com>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
daniel.vetter@ffwll.ch, tony.ye@intel.com, zhengguo.xu@intel.com
Subject: Re: [Intel-gfx] [PATCH 07/27] drm/i915/guc: Don't call switch_to_kernel_context with GuC submission
Date: Mon, 13 Sep 2021 22:02:08 -0700 [thread overview]
Message-ID: <20210914050208.GA29901@jons-linux-dev-box> (raw)
In-Reply-To: <5c023168-b32e-e6db-5b04-149a2aee1a10@intel.com>
On Mon, Sep 13, 2021 at 03:38:44PM -0700, John Harrison wrote:
> On 9/13/2021 09:54, Matthew Brost wrote:
>
> On Thu, Sep 09, 2021 at 03:51:27PM -0700, John Harrison wrote:
>
> On 8/20/2021 15:44, Matthew Brost wrote:
>
> Calling switch_to_kernel_context isn't needed if the engine PM reference
> is taken while all contexts are pinned. By not calling
> switch_to_kernel_context we save on issuing a request to the engine.
>
> I thought the intention of the switch_to_kernel was to ensure that the GPU
> is not touching any user context and is basically idle. That is not a valid
> assumption with an external scheduler such as GuC. So why is the description
> above only mentioning PM references? What is the connection between the PM
> ref and the switch_to_kernel?
>
> Also, the comment in the code does not mention anything about PM references,
> it just says 'not necessary with GuC' but no explanation at all.
>
>
> Yea, this need to be explained better. How about this?
>
> Calling switch_to_kernel_context isn't needed if the engine PM reference
> is take while all user contexts have scheduling enabled. Once scheduling
> is disabled on all user contexts the GuC is guaranteed to not touch any
> user context state which is effectively the same pointing to a kernel
> context.
>
> Matt
>
> I'm still not seeing how the PM reference is involved?
>
We shouldn't trap into the GT PM park code while a user context has
scheduling enabled as the GT PM park code may have side affects we don't
to execute if a user context still has scheduling enabled. I guess that
isn't explained very well.
> Also, IMHO the focus is wrong in the above text. The fundamental requirement is
> the ensure the hardware is idle. Execlist achieves this by switching to a safe
> context. GuC achieves it by disabling scheduling. Indeed, switching to a 'safe'
> context really has no effect with GuC submission. So 'effectively the same as
> pointing to a kernel context' is an incorrect description. I would go with
> something like:
>
> "This is execlist specific behaviour intended to ensure the GPU is idle by
> switching to a known 'safe' context. With GuC submission, the same idle
> guarantee is achieved by other means (disabling scheduling). Further,
> switching to a 'safe' context has no effect with GuC submission as the
> scheduler can just switch back again.
> FIXME: Move this backend scheduler specific behaviour into the scheduler
> backend."
>
That is worded better. Will pull into the next rev.
Matt
>
> John.
>
>
>
>
>
> v2:
> (Daniel Vetter)
> - Add FIXME comment about pushing switch_to_kernel_context to backend
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> drivers/gpu/drm/i915/gt/intel_engine_pm.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> index 1f07ac4e0672..11fee66daf60 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> @@ -162,6 +162,15 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
> unsigned long flags;
> bool result = true;
> + /*
> + * No need to switch_to_kernel_context if GuC submission
> + *
> + * FIXME: This execlists specific backend behavior in generic code, this
>
> "This execlists" -> "This is execlist"
>
> "this should be" -> "it should be"
>
> John.
>
>
> + * should be pushed to the backend.
> + */
> + if (intel_engine_uses_guc(engine))
> + return true;
> +
> /* GPU is pointing to the void, as good as in the kernel context. */
> if (intel_gt_is_wedged(engine->gt))
> return true;
>
>
> SECURITY NOTE: file ~/.netrc must not be accessible by others
next prev parent reply other threads:[~2021-09-14 5:07 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-20 22:44 [Intel-gfx] [PATCH 00/27] Parallel submission aka multi-bb execbuf Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 01/27] drm/i915/guc: Squash Clean up GuC CI failures, simplify locking, and kernel DOC Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 02/27] drm/i915/guc: Allow flexible number of context ids Matthew Brost
2021-09-09 22:13 ` John Harrison
2021-09-10 0:14 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 03/27] drm/i915/guc: Connect the number of guc_ids to debugfs Matthew Brost
2021-09-09 22:16 ` John Harrison
2021-09-10 0:16 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 04/27] drm/i915/guc: Take GT PM ref when deregistering context Matthew Brost
2021-09-09 22:28 ` John Harrison
2021-09-10 0:21 ` Matthew Brost
2021-09-13 9:55 ` Tvrtko Ursulin
2021-09-13 17:12 ` Matthew Brost
2021-09-14 8:41 ` Tvrtko Ursulin
2021-08-20 22:44 ` [Intel-gfx] [PATCH 05/27] drm/i915: Add GT PM unpark worker Matthew Brost
2021-09-09 22:36 ` John Harrison
2021-09-10 0:34 ` Matthew Brost
2021-09-10 8:36 ` Tvrtko Ursulin
2021-09-10 20:09 ` Matthew Brost
2021-09-13 10:33 ` Tvrtko Ursulin
2021-09-13 17:20 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 06/27] drm/i915/guc: Take engine PM when a context is pinned with GuC submission Matthew Brost
2021-09-09 22:46 ` John Harrison
2021-09-10 0:41 ` Matthew Brost
2021-09-13 22:26 ` John Harrison
2021-09-14 1:12 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 07/27] drm/i915/guc: Don't call switch_to_kernel_context " Matthew Brost
2021-09-09 22:51 ` John Harrison
2021-09-13 16:54 ` Matthew Brost
2021-09-13 22:38 ` John Harrison
2021-09-14 5:02 ` Matthew Brost [this message]
2021-09-13 16:55 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 08/27] drm/i915: Add logical engine mapping Matthew Brost
2021-09-10 11:12 ` Tvrtko Ursulin
2021-09-10 19:49 ` Matthew Brost
2021-09-13 9:24 ` Tvrtko Ursulin
2021-09-13 16:50 ` Matthew Brost
2021-09-14 8:34 ` Tvrtko Ursulin
2021-09-14 18:04 ` Matthew Brost
2021-09-15 8:24 ` Tvrtko Ursulin
2021-09-15 16:58 ` Matthew Brost
2021-09-16 8:31 ` Tvrtko Ursulin
2021-08-20 22:44 ` [Intel-gfx] [PATCH 09/27] drm/i915: Expose logical engine instance to user Matthew Brost
2021-09-13 23:06 ` John Harrison
2021-09-14 1:08 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 10/27] drm/i915/guc: Introduce context parent-child relationship Matthew Brost
2021-09-13 23:19 ` John Harrison
2021-09-14 1:18 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 11/27] drm/i915/guc: Implement parallel context pin / unpin functions Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 12/27] drm/i915/guc: Add multi-lrc context registration Matthew Brost
2021-09-15 19:21 ` John Harrison
2021-09-15 19:31 ` Matthew Brost
2021-09-15 20:23 ` John Harrison
2021-09-15 20:33 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 13/27] drm/i915/guc: Ensure GuC schedule operations do not operate on child contexts Matthew Brost
2021-09-15 19:24 ` John Harrison
2021-09-15 19:34 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 14/27] drm/i915/guc: Assign contexts in parent-child relationship consecutive guc_ids Matthew Brost
2021-09-15 20:04 ` John Harrison
2021-09-15 20:55 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 15/27] drm/i915/guc: Implement multi-lrc submission Matthew Brost
2021-08-21 14:04 ` kernel test robot
2021-08-22 2:18 ` kernel test robot
2021-09-20 21:48 ` John Harrison
2021-09-22 16:25 ` Matthew Brost
2021-09-22 20:15 ` John Harrison
2021-09-23 2:44 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 16/27] drm/i915/guc: Insert submit fences between requests in parent-child relationship Matthew Brost
2021-09-20 21:57 ` John Harrison
2021-08-20 22:44 ` [Intel-gfx] [PATCH 17/27] drm/i915/guc: Implement multi-lrc reset Matthew Brost
2021-09-20 22:44 ` John Harrison
2021-09-22 16:16 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 18/27] drm/i915/guc: Update debugfs for GuC multi-lrc Matthew Brost
2021-09-20 22:48 ` John Harrison
2021-09-21 19:13 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 19/27] drm/i915: Fix bug in user proto-context creation that leaked contexts Matthew Brost
2021-09-20 22:57 ` John Harrison
2021-09-21 14:49 ` Tvrtko Ursulin
2021-09-21 19:28 ` Matthew Brost
2021-09-21 19:28 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 20/27] drm/i915/guc: Connect UAPI to GuC multi-lrc interface Matthew Brost
2021-08-29 4:00 ` kernel test robot
2021-08-29 19:59 ` kernel test robot
2021-09-21 0:09 ` John Harrison
2021-09-22 16:38 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 21/27] drm/i915/doc: Update parallel submit doc to point to i915_drm.h Matthew Brost
2021-09-21 0:12 ` John Harrison
2021-08-20 22:44 ` [Intel-gfx] [PATCH 22/27] drm/i915/guc: Add basic GuC multi-lrc selftest Matthew Brost
2021-09-28 20:47 ` John Harrison
2021-08-20 22:44 ` [Intel-gfx] [PATCH 23/27] drm/i915/guc: Implement no mid batch preemption for multi-lrc Matthew Brost
2021-09-10 11:25 ` Tvrtko Ursulin
2021-09-10 20:49 ` Matthew Brost
2021-09-13 10:52 ` Tvrtko Ursulin
2021-09-28 22:20 ` John Harrison
2021-09-28 22:33 ` Matthew Brost
2021-09-28 23:33 ` John Harrison
2021-09-29 0:22 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 24/27] drm/i915: Multi-BB execbuf Matthew Brost
2021-08-21 19:01 ` kernel test robot
2021-08-30 3:46 ` kernel test robot
2021-09-30 22:16 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 25/27] drm/i915/guc: Handle errors in multi-lrc requests Matthew Brost
2021-09-29 20:44 ` John Harrison
2021-09-29 20:58 ` Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 26/27] drm/i915: Enable multi-bb execbuf Matthew Brost
2021-08-20 22:44 ` [Intel-gfx] [PATCH 27/27] drm/i915/execlists: Weak parallel submission support for execlists Matthew Brost
2021-08-20 23:13 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for Parallel submission aka multi-bb execbuf (rev3) Patchwork
2021-08-20 23:14 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2021-08-20 23:45 ` [Intel-gfx] ✗ Fi.CI.BAT: failure " Patchwork
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