From 6b071769478bdd779819163ba1ff629ca0521044 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 7 May 2020 16:23:38 +0100 Subject: [PATCH] drm/i915: Remove wait priority boosting Upon waiting a request (when asked), we gave that request a small priority boost, not enough for it to cause preemption, but enough for it to be scheduled next before all equals. We also used that bit to give new clients a small priority boost, similar to FQ_CODEL, such that we favoured short interactive tasks ahead of long running streams. However, this is causing lots of complications with timeslicing where we both want to honour the boost and yet ignore it. Those complications cause unexpected user behaviour (tasks not being timesliced and run concurrently as epxected), and the easiest way to resolve that is to remove the boost. Hopefully, we can find a compromise again if we need to, but in theory timeslicing itself and future more advanced schedulers should give us the interactivity boost we seek. Testcase: igt/gem_exec_schedule/lateslice Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200507152338.7452-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 9 --------- drivers/gpu/drm/i915/gt/intel_lrc.c | 4 +--- drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 2 +- drivers/gpu/drm/i915/i915_priolist_types.h | 7 ++----- drivers/gpu/drm/i915/i915_request.c | 3 --- drivers/gpu/drm/i915/i915_scheduler.c | 12 +----------- 6 files changed, 5 insertions(+), 32 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 966523a8503f1..d54a4933cc057 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -2597,15 +2597,6 @@ static void eb_request_add(struct i915_execbuffer *eb) */ if (!(rq->sched.flags & I915_SCHED_HAS_SEMAPHORE_CHAIN)) attr.priority |= I915_PRIORITY_NOSEMAPHORE; - - /* - * Boost priorities to new clients (new request flows). - * - * Allow interactive/synchronous clients to jump ahead of - * the bulk clients. (FQ_CODEL) - */ - if (list_empty(&rq->sched.signalers_list)) - attr.priority |= I915_PRIORITY_WAIT; } else { /* Serialise with context_close via the add_to_timeline */ i915_request_set_error_once(rq, -ENOENT); diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index dd0fd4c4cf322..59c99e2f02573 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -438,9 +438,7 @@ static int effective_prio(const struct i915_request *rq) if (__i915_request_has_started(rq)) prio |= I915_PRIORITY_NOSEMAPHORE; - /* Restrict mere WAIT boosts from triggering preemption */ - BUILD_BUG_ON(__NO_PREEMPTION & ~I915_PRIORITY_MASK); /* only internal */ - return prio | __NO_PREEMPTION; + return prio; } static int queue_prio(const struct intel_engine_execlists *execlists) diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c index aa6d56e25a10a..94eb63f309cef 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -258,7 +258,7 @@ static void guc_submit(struct intel_engine_cs *engine, static inline int rq_prio(const struct i915_request *rq) { - return rq->sched.attr.priority | __NO_PREEMPTION; + return rq->sched.attr.priority; } static struct i915_request *schedule_in(struct i915_request *rq, int idx) diff --git a/drivers/gpu/drm/i915/i915_priolist_types.h b/drivers/gpu/drm/i915/i915_priolist_types.h index 732aad1488813..e18723d8df86b 100644 --- a/drivers/gpu/drm/i915/i915_priolist_types.h +++ b/drivers/gpu/drm/i915/i915_priolist_types.h @@ -24,14 +24,13 @@ enum { I915_PRIORITY_DISPLAY, }; -#define I915_USER_PRIORITY_SHIFT 2 +#define I915_USER_PRIORITY_SHIFT 1 #define I915_USER_PRIORITY(x) ((x) << I915_USER_PRIORITY_SHIFT) #define I915_PRIORITY_COUNT BIT(I915_USER_PRIORITY_SHIFT) #define I915_PRIORITY_MASK (I915_PRIORITY_COUNT - 1) -#define I915_PRIORITY_WAIT ((u8)BIT(0)) -#define I915_PRIORITY_NOSEMAPHORE ((u8)BIT(1)) +#define I915_PRIORITY_NOSEMAPHORE ((u8)BIT(0)) /* Smallest priority value that cannot be bumped. */ #define I915_PRIORITY_INVALID (INT_MIN | (u8)I915_PRIORITY_MASK) @@ -47,8 +46,6 @@ enum { #define I915_PRIORITY_UNPREEMPTABLE INT_MAX #define I915_PRIORITY_BARRIER INT_MAX -#define __NO_PREEMPTION (I915_PRIORITY_WAIT) - struct i915_priolist { struct list_head requests[I915_PRIORITY_COUNT]; struct rb_node node; diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 3c38d61c90f82..589739bfee25a 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -1464,8 +1464,6 @@ void i915_request_add(struct i915_request *rq) if (!(rq->sched.flags & I915_SCHED_HAS_SEMAPHORE_CHAIN)) attr.priority |= I915_PRIORITY_NOSEMAPHORE; - if (list_empty(&rq->sched.signalers_list)) - attr.priority |= I915_PRIORITY_WAIT; __i915_request_queue(rq, &attr); @@ -1651,7 +1649,6 @@ long i915_request_wait(struct i915_request *rq, if (flags & I915_WAIT_PRIORITY) { if (!i915_request_started(rq) && INTEL_GEN(rq->i915) >= 6) intel_rps_boost(rq); - i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT); } wait.tsk = current; diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c index 6e2d4190099fb..bec2a9c254257 100644 --- a/drivers/gpu/drm/i915/i915_scheduler.c +++ b/drivers/gpu/drm/i915/i915_scheduler.c @@ -174,7 +174,7 @@ sched_lock_engine(const struct i915_sched_node *node, static inline int rq_prio(const struct i915_request *rq) { - return rq->sched.attr.priority | __NO_PREEMPTION; + return rq->sched.attr.priority; } static inline bool need_preempt(int prio, int active) @@ -443,16 +443,6 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, list_add_rcu(&dep->signal_link, &node->signalers_list); list_add_rcu(&dep->wait_link, &signal->waiters_list); - /* - * As we do not allow WAIT to preempt inflight requests, - * once we have executed a request, along with triggering - * any execution callbacks, we must preserve its ordering - * within the non-preemptible FIFO. - */ - BUILD_BUG_ON(__NO_PREEMPTION & ~I915_PRIORITY_MASK); - if (flags & I915_DEPENDENCY_EXTERNAL) - __bump_priority(signal, __NO_PREEMPTION); - ret = true; } -- 2.39.5