Commit d9948a10 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Remove second level open-coded rcu work 



We currently use a worker queued from an rcu callback to determine when
a how grace period has elapsed while we remained idle. We use this idle
delay to infer that we will be idle for a while and this is a suitable
point at which we can trim our global memory caches.

Since we wrote that, this mechanism now exists as rcu_work, and having
converted the idle shrinkers over to using that, we can remove our own
variant.

v2: Say goodbye to gt.epoch as well.
v3: Remove the misplaced and redundant comment before parking globals

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190228102035.5857-3-chris@chris-wilson.co.uk
parent 13f1bfd3

drivers/gpu/drm/i915/i915_debugfs.c

+2 −4
Original line number Diff line number Diff line
@@ -2655,8 +2655,7 @@ static int i915_runtime_pm_status(struct seq_file *m, void *unused) 
	seq_printf(m, "Runtime power status: %s\n",

		   enableddisabled(!dev_priv->power_domains.wakeref));



	seq_printf(m, "GPU idle: %s (epoch %u)\n",

		   yesno(!dev_priv->gt.awake), dev_priv->gt.epoch);

	seq_printf(m, "GPU idle: %s\n", yesno(!dev_priv->gt.awake));

	seq_printf(m, "IRQs disabled: %s\n",

		   yesno(!intel_irqs_enabled(dev_priv)));

#ifdef CONFIG_PM
@@ -3092,8 +3091,7 @@ static int i915_engine_info(struct seq_file *m, void *unused) 


	wakeref = intel_runtime_pm_get(dev_priv);



	seq_printf(m, "GT awake? %s (epoch %u)\n",

		   yesno(dev_priv->gt.awake), dev_priv->gt.epoch);

	seq_printf(m, "GT awake? %s\n", yesno(dev_priv->gt.awake));

	seq_printf(m, "Global active requests: %d\n",

		   dev_priv->gt.active_requests);

	seq_printf(m, "CS timestamp frequency: %u kHz\n",

drivers/gpu/drm/i915/i915_drv.h

+0 −6
Original line number Diff line number Diff line
@@ -2005,12 +2005,6 @@ struct drm_i915_private { 
		 */

		intel_wakeref_t awake;



		/**

		 * The number of times we have woken up.

		 */

		unsigned int epoch;

#define I915_EPOCH_INVALID 0



		/**

		 * We leave the user IRQ off as much as possible,

		 * but this means that requests will finish and never

drivers/gpu/drm/i915/i915_gem.c

+4 −84
Original line number Diff line number Diff line
@@ -101,7 +101,7 @@ static void i915_gem_info_remove_obj(struct drm_i915_private *dev_priv, 
	spin_unlock(&dev_priv->mm.object_stat_lock);

}



static u32 __i915_gem_park(struct drm_i915_private *i915)

static void __i915_gem_park(struct drm_i915_private *i915)

{

	intel_wakeref_t wakeref;
@@ -112,9 +112,7 @@ static u32 __i915_gem_park(struct drm_i915_private *i915) 
	GEM_BUG_ON(!list_empty(&i915->gt.active_rings));



	if (!i915->gt.awake)

		return I915_EPOCH_INVALID;



	GEM_BUG_ON(i915->gt.epoch == I915_EPOCH_INVALID);

		return;



	/*

	 * Be paranoid and flush a concurrent interrupt to make sure
@@ -143,7 +141,7 @@ static u32 __i915_gem_park(struct drm_i915_private *i915) 


	intel_display_power_put(i915, POWER_DOMAIN_GT_IRQ, wakeref);



	return i915->gt.epoch;

	i915_globals_park();

}



void i915_gem_park(struct drm_i915_private *i915)
@@ -185,9 +183,6 @@ void i915_gem_unpark(struct drm_i915_private *i915) 
	i915->gt.awake = intel_display_power_get(i915, POWER_DOMAIN_GT_IRQ);

	GEM_BUG_ON(!i915->gt.awake);



	if (unlikely(++i915->gt.epoch == 0)) /* keep 0 as invalid */

		i915->gt.epoch = 1;



	i915_globals_unpark();



	intel_enable_gt_powersave(i915);
@@ -2877,62 +2872,6 @@ i915_gem_retire_work_handler(struct work_struct *work) 
				   round_jiffies_up_relative(HZ));

}



static void shrink_caches(struct drm_i915_private *i915)

{

	/*

	 * kmem_cache_shrink() discards empty slabs and reorders partially

	 * filled slabs to prioritise allocating from the mostly full slabs,

	 * with the aim of reducing fragmentation.

	 */

	i915_globals_park();

}



struct sleep_rcu_work {

	union {

		struct rcu_head rcu;

		struct work_struct work;

	};

	struct drm_i915_private *i915;

	unsigned int epoch;

};



static inline bool

same_epoch(struct drm_i915_private *i915, unsigned int epoch)

{

	/*

	 * There is a small chance that the epoch wrapped since we started

	 * sleeping. If we assume that epoch is at least a u32, then it will

	 * take at least 2^32 * 100ms for it to wrap, or about 326 years.

	 */

	return epoch == READ_ONCE(i915->gt.epoch);

}



static void __sleep_work(struct work_struct *work)

{

	struct sleep_rcu_work *s = container_of(work, typeof(*s), work);

	struct drm_i915_private *i915 = s->i915;

	unsigned int epoch = s->epoch;



	kfree(s);

	if (same_epoch(i915, epoch))

		shrink_caches(i915);

}



static void __sleep_rcu(struct rcu_head *rcu)

{

	struct sleep_rcu_work *s = container_of(rcu, typeof(*s), rcu);

	struct drm_i915_private *i915 = s->i915;



	destroy_rcu_head(&s->rcu);



	if (same_epoch(i915, s->epoch)) {

		INIT_WORK(&s->work, __sleep_work);

		queue_work(i915->wq, &s->work);

	} else {

		kfree(s);

	}

}



static inline bool

new_requests_since_last_retire(const struct drm_i915_private *i915)

{
@@ -2961,7 +2900,6 @@ i915_gem_idle_work_handler(struct work_struct *work) 
{

	struct drm_i915_private *dev_priv =

		container_of(work, typeof(*dev_priv), gt.idle_work.work);

	unsigned int epoch = I915_EPOCH_INVALID;

	bool rearm_hangcheck;



	if (!READ_ONCE(dev_priv->gt.awake))
@@ -3016,7 +2954,7 @@ i915_gem_idle_work_handler(struct work_struct *work) 
	if (new_requests_since_last_retire(dev_priv))

		goto out_unlock;



	epoch = __i915_gem_park(dev_priv);

	__i915_gem_park(dev_priv);



	assert_kernel_context_is_current(dev_priv);
@@ -3029,24 +2967,6 @@ out_rearm: 
		GEM_BUG_ON(!dev_priv->gt.awake);

		i915_queue_hangcheck(dev_priv);

	}



	/*

	 * When we are idle, it is an opportune time to reap our caches.

	 * However, we have many objects that utilise RCU and the ordered

	 * i915->wq that this work is executing on. To try and flush any

	 * pending frees now we are idle, we first wait for an RCU grace

	 * period, and then queue a task (that will run last on the wq) to

	 * shrink and re-optimize the caches.

	 */

	if (same_epoch(dev_priv, epoch)) {

		struct sleep_rcu_work *s = kmalloc(sizeof(*s), GFP_KERNEL);

		if (s) {

			init_rcu_head(&s->rcu);

			s->i915 = dev_priv;

			s->epoch = epoch;

			call_rcu(&s->rcu, __sleep_rcu);

		}

	}

}



void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file)

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