From df403069029dc61e0fc09cbeb0b5900705edec5b Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 16 Aug 2019 18:16:08 +0100 Subject: [PATCH] drm/i915/execlists: Lift process_csb() out of the irq-off spinlock If we only call process_csb() from the tasklet, though we lose the ability to bypass ksoftirqd interrupt processing on direct submission paths, we can push it out of the irq-off spinlock. The penalty is that we then allow schedule_out to be called concurrently with schedule_in requiring us to handle the usage count (baked into the pointer itself) atomically. As we do kick the tasklets (via local_bh_enable()) after our submission, there is a possibility there to see if we can pull the local softirq processing back from the ksoftirqd. v2: Store the 'switch_priority_hint' on submission, so that we can safely check during process_csb(). Signed-off-by: Chris Wilson Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20190816171608.11760-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_context_types.h | 4 +- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 2 +- drivers/gpu/drm/i915/gt/intel_engine_types.h | 10 ++ drivers/gpu/drm/i915/gt/intel_lrc.c | 136 ++++++++++++++++---------- drivers/gpu/drm/i915/i915_utils.h | 20 ++-- 5 files changed, 108 insertions(+), 64 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h index 616f3f9a6825..bf9cedfccbf0 100644 --- a/drivers/gpu/drm/i915/gt/intel_context_types.h +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h @@ -41,9 +41,7 @@ struct intel_context { struct intel_engine_cs *engine; struct intel_engine_cs *inflight; #define intel_context_inflight(ce) ptr_mask_bits((ce)->inflight, 2) -#define intel_context_inflight_count(ce) ptr_unmask_bits((ce)->inflight, 2) -#define intel_context_inflight_inc(ce) ptr_count_inc(&(ce)->inflight) -#define intel_context_inflight_dec(ce) ptr_count_dec(&(ce)->inflight) +#define intel_context_inflight_count(ce) ptr_unmask_bits((ce)->inflight, 2) struct i915_address_space *vm; struct i915_gem_context *gem_context; diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index 957f27a2ec97..ba457c1c7dc0 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -1459,7 +1459,7 @@ int intel_enable_engine_stats(struct intel_engine_cs *engine) for (port = execlists->pending; (rq = *port); port++) { /* Exclude any contexts already counted in active */ - if (intel_context_inflight_count(rq->hw_context) == 1) + if (!intel_context_inflight_count(rq->hw_context)) engine->stats.active++; } diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h index 9965a32601d6..5441aa9cb863 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h @@ -205,6 +205,16 @@ struct intel_engine_execlists { unsigned int port_mask; /** + * @switch_priority_hint: Second context priority. + * + * We submit multiple contexts to the HW simultaneously and would + * like to occasionally switch between them to emulate timeslicing. + * To know when timeslicing is suitable, we track the priority of + * the context submitted second. + */ + int switch_priority_hint; + + /** * @queue_priority_hint: Highest pending priority. * * When we add requests into the queue, or adjust the priority of diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index e9863f4d826b..2978cf16fb9b 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -547,27 +547,39 @@ execlists_context_status_change(struct i915_request *rq, unsigned long status) status, rq); } +static inline struct intel_engine_cs * +__execlists_schedule_in(struct i915_request *rq) +{ + struct intel_engine_cs * const engine = rq->engine; + struct intel_context * const ce = rq->hw_context; + + intel_context_get(ce); + + intel_gt_pm_get(engine->gt); + execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN); + intel_engine_context_in(engine); + + return engine; +} + static inline struct i915_request * execlists_schedule_in(struct i915_request *rq, int idx) { - struct intel_context *ce = rq->hw_context; - int count; + struct intel_context * const ce = rq->hw_context; + struct intel_engine_cs *old; + GEM_BUG_ON(!intel_engine_pm_is_awake(rq->engine)); trace_i915_request_in(rq, idx); - count = intel_context_inflight_count(ce); - if (!count) { - intel_context_get(ce); - ce->inflight = rq->engine; - - intel_gt_pm_get(ce->inflight->gt); - execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN); - intel_engine_context_in(ce->inflight); - } + old = READ_ONCE(ce->inflight); + do { + if (!old) { + WRITE_ONCE(ce->inflight, __execlists_schedule_in(rq)); + break; + } + } while (!try_cmpxchg(&ce->inflight, &old, ptr_inc(old))); - intel_context_inflight_inc(ce); GEM_BUG_ON(intel_context_inflight(ce) != rq->engine); - return i915_request_get(rq); } @@ -581,35 +593,45 @@ static void kick_siblings(struct i915_request *rq, struct intel_context *ce) } static inline void -execlists_schedule_out(struct i915_request *rq) +__execlists_schedule_out(struct i915_request *rq, + struct intel_engine_cs * const engine) { - struct intel_context *ce = rq->hw_context; + struct intel_context * const ce = rq->hw_context; - GEM_BUG_ON(!intel_context_inflight_count(ce)); + intel_engine_context_out(engine); + execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT); + intel_gt_pm_put(engine->gt); - trace_i915_request_out(rq); + /* + * If this is part of a virtual engine, its next request may + * have been blocked waiting for access to the active context. + * We have to kick all the siblings again in case we need to + * switch (e.g. the next request is not runnable on this + * engine). Hopefully, we will already have submitted the next + * request before the tasklet runs and do not need to rebuild + * each virtual tree and kick everyone again. + */ + if (ce->engine != engine) + kick_siblings(rq, ce); - intel_context_inflight_dec(ce); - if (!intel_context_inflight_count(ce)) { - intel_engine_context_out(ce->inflight); - execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT); - intel_gt_pm_put(ce->inflight->gt); + intel_context_put(ce); +} - /* - * If this is part of a virtual engine, its next request may - * have been blocked waiting for access to the active context. - * We have to kick all the siblings again in case we need to - * switch (e.g. the next request is not runnable on this - * engine). Hopefully, we will already have submitted the next - * request before the tasklet runs and do not need to rebuild - * each virtual tree and kick everyone again. - */ - ce->inflight = NULL; - if (rq->engine != ce->engine) - kick_siblings(rq, ce); +static inline void +execlists_schedule_out(struct i915_request *rq) +{ + struct intel_context * const ce = rq->hw_context; + struct intel_engine_cs *cur, *old; - intel_context_put(ce); - } + trace_i915_request_out(rq); + GEM_BUG_ON(intel_context_inflight(ce) != rq->engine); + + old = READ_ONCE(ce->inflight); + do + cur = ptr_unmask_bits(old, 2) ? ptr_dec(old) : NULL; + while (!try_cmpxchg(&ce->inflight, &old, cur)); + if (!cur) + __execlists_schedule_out(rq, old); i915_request_put(rq); } @@ -684,6 +706,9 @@ assert_pending_valid(const struct intel_engine_execlists *execlists, trace_ports(execlists, msg, execlists->pending); + if (!execlists->pending[0]) + return false; + if (execlists->pending[execlists_num_ports(execlists)]) return false; @@ -941,12 +966,24 @@ need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq) return hint >= effective_prio(rq); } +static int +switch_prio(struct intel_engine_cs *engine, const struct i915_request *rq) +{ + if (list_is_last(&rq->sched.link, &engine->active.requests)) + return INT_MIN; + + return rq_prio(list_next_entry(rq, sched.link)); +} + static bool -enable_timeslice(struct intel_engine_cs *engine) +enable_timeslice(const struct intel_engine_execlists *execlists) { - struct i915_request *last = last_active(&engine->execlists); + const struct i915_request *rq = *execlists->active; - return last && need_timeslice(engine, last); + if (i915_request_completed(rq)) + return false; + + return execlists->switch_priority_hint >= effective_prio(rq); } static void record_preemption(struct intel_engine_execlists *execlists) @@ -1292,6 +1329,8 @@ done: *port = execlists_schedule_in(last, port - execlists->pending); memset(port + 1, 0, (last_port - port) * sizeof(*port)); execlists_submit_ports(engine); + execlists->switch_priority_hint = + switch_prio(engine, *execlists->pending); } else { ring_set_paused(engine, 0); } @@ -1356,7 +1395,6 @@ static void process_csb(struct intel_engine_cs *engine) const u8 num_entries = execlists->csb_size; u8 head, tail; - lockdep_assert_held(&engine->active.lock); GEM_BUG_ON(USES_GUC_SUBMISSION(engine->i915)); /* @@ -1427,15 +1465,14 @@ static void process_csb(struct intel_engine_cs *engine) execlists->pending, execlists_num_ports(execlists) * sizeof(*execlists->pending)); - execlists->pending[0] = NULL; - trace_ports(execlists, "promoted", execlists->active); - - if (enable_timeslice(engine)) + if (enable_timeslice(execlists)) mod_timer(&execlists->timer, jiffies + 1); if (!inject_preempt_hang(execlists)) ring_set_paused(engine, 0); + + WRITE_ONCE(execlists->pending[0], NULL); break; case CSB_COMPLETE: /* port0 completed, advanced to port1 */ @@ -1479,8 +1516,6 @@ static void process_csb(struct intel_engine_cs *engine) static void __execlists_submission_tasklet(struct intel_engine_cs *const engine) { lockdep_assert_held(&engine->active.lock); - - process_csb(engine); if (!engine->execlists.pending[0]) execlists_dequeue(engine); } @@ -1494,9 +1529,12 @@ static void execlists_submission_tasklet(unsigned long data) struct intel_engine_cs * const engine = (struct intel_engine_cs *)data; unsigned long flags; - spin_lock_irqsave(&engine->active.lock, flags); - __execlists_submission_tasklet(engine); - spin_unlock_irqrestore(&engine->active.lock, flags); + process_csb(engine); + if (!READ_ONCE(engine->execlists.pending[0])) { + spin_lock_irqsave(&engine->active.lock, flags); + __execlists_submission_tasklet(engine); + spin_unlock_irqrestore(&engine->active.lock, flags); + } } static void execlists_submission_timer(struct timer_list *timer) diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h index d652ba5d2320..562f756da421 100644 --- a/drivers/gpu/drm/i915/i915_utils.h +++ b/drivers/gpu/drm/i915/i915_utils.h @@ -161,17 +161,15 @@ __check_struct_size(size_t base, size_t arr, size_t count, size_t *size) ((typeof(ptr))((unsigned long)(ptr) | __bits)); \ }) -#define ptr_count_dec(p_ptr) do { \ - typeof(p_ptr) __p = (p_ptr); \ - unsigned long __v = (unsigned long)(*__p); \ - *__p = (typeof(*p_ptr))(--__v); \ -} while (0) - -#define ptr_count_inc(p_ptr) do { \ - typeof(p_ptr) __p = (p_ptr); \ - unsigned long __v = (unsigned long)(*__p); \ - *__p = (typeof(*p_ptr))(++__v); \ -} while (0) +#define ptr_dec(ptr) ({ \ + unsigned long __v = (unsigned long)(ptr); \ + (typeof(ptr))(__v - 1); \ +}) + +#define ptr_inc(ptr) ({ \ + unsigned long __v = (unsigned long)(ptr); \ + (typeof(ptr))(__v + 1); \ +}) #define page_mask_bits(ptr) ptr_mask_bits(ptr, PAGE_SHIFT) #define page_unmask_bits(ptr) ptr_unmask_bits(ptr, PAGE_SHIFT) -- 2.11.0