On 27/02/2019 23:09, Chris Wilson wrote:
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.
By the look of it gt.epoch can be completely ripped out.
Regards,
Tvrtko
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_gem.c | 91 +++++----------------------------
1 file changed, 12 insertions(+), 79 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 8ded7e1756c9..8cf3429594d5 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -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;
@@ -112,7 +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;
+ return;
GEM_BUG_ON(i915->gt.epoch == I915_EPOCH_INVALID);
@@ -143,7 +143,15 @@ static u32 __i915_gem_park(struct drm_i915_private *i915)
intel_display_power_put(i915, POWER_DOMAIN_GT_IRQ, wakeref);
- return i915->gt.epoch;
+ /*
+ * 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.
+ */
+ i915_globals_park();
}
void i915_gem_park(struct drm_i915_private *i915)
@@ -2877,62 +2885,6 @@ 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 +2913,6 @@ 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 +2967,7 @@ 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 +2980,6 @@ i915_gem_idle_work_handler(struct work_struct *work)
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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