Commit f530a41d authored by Chris Wilson's avatar Chris Wilson
Browse files

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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarAndi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115142331.24458-3-chris@chris-wilson.co.uk
parent 4fb05a39

drivers/gpu/drm/i915/gt/intel_engine_cs.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

}

drivers/gpu/drm/i915/gt/intel_engine_stats.h

+28 −17
Original line number Diff line number Diff line
@@ -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;

	}



	/* The writer is serialised; but the pmu reader may be from hardirq */

	local_irq_save(flags);

	write_seqcount_begin(&engine->stats.lock);



	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);

	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;

	}



	local_irq_save(flags);

	write_seqcount_begin(&engine->stats.lock);



	write_seqlock_irqsave(&engine->stats.lock, flags);

	if (atomic_dec_and_test(&engine->stats.active)) {

	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);



	write_seqcount_end(&engine->stats.lock);

	local_irq_restore(flags);

}



#endif /* __INTEL_ENGINE_STATS_H__ */

drivers/gpu/drm/i915/gt/intel_engine_types.h

+2 −2
Original line number Diff line number Diff line
@@ -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.