On 2018-10-16 12:53, Joonas Lahtinen wrote:
Quoting Tomasz Lis (2018-10-15 20:29:18)The patch adds support of preempt-to-idle requesting by setting a proper bit within Execlist Control Register, and receiving preemption result from Context Status Buffer. Preemption in previous gens required a special batch buffer to be executed, so the Command Streamer never preempted to idle directly. In Icelake it is possible, as there is a hardware mechanism to inform the kernel about status of the preemption request. This patch does not cover using the new preemption mechanism when GuC is active. v2: Added needs_preempt_context() change so that it is not created when preempt-to-idle is supported. (Chris) Updated setting HWACK flag so that it is cleared after preempt-to-dle. (Chris, Daniele) Updated to use I915_ENGINE_HAS_PREEMPTION flag. (Chris) v3: Fixed needs_preempt_context() change. (Chris) Merged preemption trigger functions to one. (Chris) Fixed conyext state tonot assume COMPLETED_MASK after preemption, since idle-to-idle case will not have it set. v4: Simplified needs_preempt_context() change. (Daniele) Removed clearing HWACK flag in idle-to-idle preempt. (Daniele) v5: Renamed inject_preempt_context(). (Daniele) Removed duplicated GEM_BUG_ON() on HWACK (Daniele) Bspec: 18922 Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx> Cc: Michal Winiarski <michal.winiarski@xxxxxxxxx> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>This R-b was on v4, and should be indicated with # v4 comment. The commit message doesn't say much about why preempting to idle is beneficial? The pre-Gen11 codepath needs to be maintained anyway. Regards, Joonas
The benefit is one less context switch - there is no "preempt context". -Tomasz _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
