From f530a41d13f2f45174fa0996a85edc32278d3fd5 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 15 Jan 2021 14:23:29 +0000 Subject: [PATCH] drm/i915/gt: Convert stats.active to plain unsigned int As context-in/out is now always serialised, we do not have to worry about concurrent enabling/disable of the busy-stats and can reduce the atomic_t active to a plain unsigned int, and the seqlock to a seqcount. Signed-off-by: Chris Wilson Reviewed-by: Andi Shyti Link: https://patchwork.freedesktop.org/patch/msgid/20210115142331.24458-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 8 ++--- drivers/gpu/drm/i915/gt/intel_engine_stats.h | 45 +++++++++++++++++----------- drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 +-- 3 files changed, 34 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index ba8f8a8..fb1b1d0 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -342,7 +342,7 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id) engine->schedule = NULL; ewma__engine_latency_init(&engine->latency); - seqlock_init(&engine->stats.lock); + seqcount_init(&engine->stats.lock); ATOMIC_INIT_NOTIFIER_HEAD(&engine->context_status_notifier); @@ -1754,7 +1754,7 @@ static ktime_t __intel_engine_get_busy_time(struct intel_engine_cs *engine, * add it to the total. */ *now = ktime_get(); - if (atomic_read(&engine->stats.active)) + if (READ_ONCE(engine->stats.active)) total = ktime_add(total, ktime_sub(*now, engine->stats.start)); return total; @@ -1773,9 +1773,9 @@ ktime_t intel_engine_get_busy_time(struct intel_engine_cs *engine, ktime_t *now) ktime_t total; do { - seq = read_seqbegin(&engine->stats.lock); + seq = read_seqcount_begin(&engine->stats.lock); total = __intel_engine_get_busy_time(engine, now); - } while (read_seqretry(&engine->stats.lock, seq)); + } while (read_seqcount_retry(&engine->stats.lock, seq)); return total; } diff --git a/drivers/gpu/drm/i915/gt/intel_engine_stats.h b/drivers/gpu/drm/i915/gt/intel_engine_stats.h index 58491ea..24fbdd9 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_stats.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_stats.h @@ -17,33 +17,44 @@ static inline void intel_engine_context_in(struct intel_engine_cs *engine) { unsigned long flags; - if (atomic_add_unless(&engine->stats.active, 1, 0)) + if (engine->stats.active) { + engine->stats.active++; return; - - write_seqlock_irqsave(&engine->stats.lock, flags); - if (!atomic_add_unless(&engine->stats.active, 1, 0)) { - engine->stats.start = ktime_get(); - atomic_inc(&engine->stats.active); } - write_sequnlock_irqrestore(&engine->stats.lock, flags); + + /* The writer is serialised; but the pmu reader may be from hardirq */ + local_irq_save(flags); + write_seqcount_begin(&engine->stats.lock); + + engine->stats.start = ktime_get(); + engine->stats.active++; + + write_seqcount_end(&engine->stats.lock); + local_irq_restore(flags); + + GEM_BUG_ON(!engine->stats.active); } static inline void intel_engine_context_out(struct intel_engine_cs *engine) { unsigned long flags; - GEM_BUG_ON(!atomic_read(&engine->stats.active)); - - if (atomic_add_unless(&engine->stats.active, -1, 1)) + GEM_BUG_ON(!engine->stats.active); + if (engine->stats.active > 1) { + engine->stats.active--; return; - - write_seqlock_irqsave(&engine->stats.lock, flags); - if (atomic_dec_and_test(&engine->stats.active)) { - engine->stats.total = - ktime_add(engine->stats.total, - ktime_sub(ktime_get(), engine->stats.start)); } - write_sequnlock_irqrestore(&engine->stats.lock, flags); + + local_irq_save(flags); + write_seqcount_begin(&engine->stats.lock); + + engine->stats.active--; + engine->stats.total = + ktime_add(engine->stats.total, + ktime_sub(ktime_get(), engine->stats.start)); + + write_seqcount_end(&engine->stats.lock); + local_irq_restore(flags); } #endif /* __INTEL_ENGINE_STATS_H__ */ diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h index 75c9093..d2346b4 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h @@ -516,12 +516,12 @@ struct intel_engine_cs { /** * @active: Number of contexts currently scheduled in. */ - atomic_t active; + unsigned int active; /** * @lock: Lock protecting the below fields. */ - seqlock_t lock; + seqcount_t lock; /** * @total: Total time this engine was busy. -- 2.7.4