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authorChris Wilson <chris@chris-wilson.co.uk>2019-02-28 22:06:39 +0000
committerChris Wilson <chris@chris-wilson.co.uk>2019-02-28 23:10:43 +0000
commitb5773a3616d10bdef60662b8780ded912ee5d7b6 (patch)
tree4f07f7291f9678e23d4c7e56701978c4be5700c8 /drivers/gpu/drm/i915/intel_lrc.c
parentbd5d6781a0f1b9be8c26da78c0e3110e7481b45b (diff)
downloadlwn-b5773a3616d10bdef60662b8780ded912ee5d7b6.tar.gz
lwn-b5773a3616d10bdef60662b8780ded912ee5d7b6.zip
drm/i915/execlists: Suppress mere WAIT preemption
WAIT is occasionally suppressed by virtue of preempted requests being promoted to NEWCLIENT if they have not all ready received that boost. Make this consistent for all WAIT boosts that they are not allowed to preempt executing contexts and are merely granted the right to be at the front of the queue for the next execution slot. This is in keeping with the desire that the WAIT boost be a minor tweak that does not give excessive promotion to its user and open ourselves to trivial abuse. The problem with the inconsistent WAIT preemption becomes more apparent as the preemption is propagated across the engines, where one engine may preempt and the other not, and we be relying on the exact execution order being consistent across engines (e.g. using HW semaphores to coordinate parallel execution). v2: Also protect GuC submission from false preemption loops. v3: Build bug safeguards and better debug messages for st. v4: Do the priority bumping in unsubmit (i.e. on preemption/reset unwind), applying it earlier during submit causes out-of-order execution combined with execute fences. v5: Call sw_fence_fini for our dummy request (Matthew) Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Matthew Auld <matthew.auld@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190228220639.3173-1-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/intel_lrc.c')
-rw-r--r--drivers/gpu/drm/i915/intel_lrc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 661d2f6da84f..4f2187aa44e4 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -188,6 +188,12 @@ static inline int rq_prio(const struct i915_request *rq)
return rq->sched.attr.priority;
}
+static int effective_prio(const struct i915_request *rq)
+{
+ /* Restrict mere WAIT boosts from triggering preemption */
+ return rq_prio(rq) | __NO_PREEMPTION;
+}
+
static int queue_prio(const struct intel_engine_execlists *execlists)
{
struct i915_priolist *p;
@@ -208,7 +214,7 @@ static int queue_prio(const struct intel_engine_execlists *execlists)
static inline bool need_preempt(const struct intel_engine_cs *engine,
const struct i915_request *rq)
{
- const int last_prio = rq_prio(rq);
+ int last_prio;
if (!intel_engine_has_preemption(engine))
return false;
@@ -228,6 +234,7 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
* preempt. If that hint is stale or we may be trying to preempt
* ourselves, ignore the request.
*/
+ last_prio = effective_prio(rq);
if (!__execlists_need_preempt(engine->execlists.queue_priority_hint,
last_prio))
return false;