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01 Jun 2021 03:09:49 -0700 To: Daniel Vetter References: <20210525135508.244659-1-tejaskumarx.surendrakumar.upadhyay@intel.com> <20210525135508.244659-2-tejaskumarx.surendrakumar.upadhyay@intel.com> <8cf2c5f4-87a3-ce6b-150c-65fa054586a4@linux.intel.com> <59d2eee9-35c1-01fc-c226-50ad98aadb99@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: Date: Tue, 1 Jun 2021 11:09:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Subject: Re: [Intel-gfx] [PATCH 1/1] Let userspace know if they can trust timeslicing by including it as part of the I915_PARAM_HAS_SCHEDULER::I915_SCHEDULER_CAP_TIMESLICING X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, DRI Development , mahesh.meena@intel.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 27/05/2021 11:27, Daniel Vetter wrote: > On Thu, May 27, 2021 at 11:22:16AM +0100, Tvrtko Ursulin wrote: >> >> On 27/05/2021 11:13, Daniel Vetter wrote: >>> On Wed, May 26, 2021 at 11:20:13AM +0100, Tvrtko Ursulin wrote: >>>> >>>> On 25/05/2021 15:47, Daniel Vetter wrote: >>>>> On Tue, May 25, 2021 at 03:19:47PM +0100, Tvrtko Ursulin wrote: >>>>>> >>>>>> + dri-devel as per process >>>>>> >>>>>> On 25/05/2021 14:55, Tejas Upadhyay wrote: >>>>>>> v2: Only declare timeslicing if we can safely preempt userspace. >>>>>> >>>>>> Commit message got butchered up somehow so you'll need to fix that at some >>>>>> point. >>>>>> >>>>>> Regards, >>>>>> >>>>>> Tvrtko >>>>>> >>>>>>> Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing") >>>>>>> Signed-off-by: Chris Wilson >>>>>>> Cc: Tvrtko Ursulin >>>>>>> Reviewed-by: Tvrtko Ursulin >>>>>>> --- >>>>>>> drivers/gpu/drm/i915/gt/intel_engine_user.c | 1 + >>>>>>> include/uapi/drm/i915_drm.h | 1 + >>>>>>> 2 files changed, 2 insertions(+) >>>>>>> >>>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c >>>>>>> index 3cca7ea2d6ea..12d165566ed2 100644 >>>>>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c >>>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c >>>>>>> @@ -98,6 +98,7 @@ static void set_scheduler_caps(struct drm_i915_private *i915) >>>>>>> MAP(HAS_PREEMPTION, PREEMPTION), >>>>>>> MAP(HAS_SEMAPHORES, SEMAPHORES), >>>>>>> MAP(SUPPORTS_STATS, ENGINE_BUSY_STATS), >>>>>>> + MAP(TIMESLICE_BIT, TIMESLICING), >>>>>>> #undef MAP >>>>>>> }; >>>>>>> struct intel_engine_cs *engine; >>>>>>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h >>>>>>> index c2c7759b7d2e..af2212d6113c 100644 >>>>>>> --- a/include/uapi/drm/i915_drm.h >>>>>>> +++ b/include/uapi/drm/i915_drm.h >>>>>>> @@ -572,6 +572,7 @@ typedef struct drm_i915_irq_wait { >>>>>>> #define I915_SCHEDULER_CAP_PREEMPTION (1ul << 2) >>>>>>> #define I915_SCHEDULER_CAP_SEMAPHORES (1ul << 3) >>>>>>> #define I915_SCHEDULER_CAP_ENGINE_BUSY_STATS (1ul << 4) >>>>>>> +#define I915_SCHEDULER_CAP_TIMESLICING (1ul << 5) >>>>> >>>>> Since this is uapi I think we should at least have some nice kerneldoc >>>>> that explains what exactly this is, what for (link to userspace) and all >>>>> that. Ideally also minimally filing in the gaps in our uapi docs for stuff >>>>> this references. >>>> >>>> IIUC there is no userspace apart from IGT needing it not to fail scheduling >>>> tests on ADL. >>>> >>>> Current tests use "has preemption + has semaphores" as a proxy to answer the >>>> "does the kernel support timeslicing" question. This stops working with the >>>> Guc backend because GuC decided not to support semaphores (for reasons yet >>>> unknown, see other thread), so explicit "has timeslicing" flag is needed in >>>> order for tests to know that GuC is supposed to support timeslicing, even if >>>> it doesn't use semaphores for inter-ring synchronisation. >>> >>> Since this if for igt only: Cant we do just extend the check in igt with >>> an || GEN >= 12? I really hope that our future hw will continue to support >>> timeslicing ... >> >> Not the gen 12 check, but possible I think. Explicit feature test would be better, but if definitely not allowed then along the lines of: >> >> has_timeslicing = >> (has_preemption && has_semaphores) || uses_guc_submission; > > That works too. Otoh what exactly is the "uses guc submission" flag and > why do we have that? I've seen media use it as a stand-in for "does the > kernel want bonded or parallel ctx?". Maybe another thing to check. > > Another option, if you really think the feature flag is the best approach > (because future hw will drop timeslicing for some reason), then debugfs is > the place of igt-only api. Maybe check and potentially remove all I915_SCHEDULER_CAP_.. flags. It could be another easy pickings with a lot of IGT work type endeavour. Regards, Tvrtko _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx