[Intel-gfx] [PATCH 1/2] drm/i915: Reduce recursive mutex locking from the shrinker
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Wed Jan 9 14:12:46 UTC 2019
From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
In two codepaths internal to the shrinker we know we will end up taking
the resursive mutex path.
It instead feels more elegant to avoid this altogether and not call
mutex_trylock_recursive in those cases.
We achieve this by extracting the shrinking part to __i915_gem_shrink,
wrapped by struct mutex taking i915_gem_shrink.
At the same time move the runtime pm reference taking to always be in the
usual, before struct mutex, order.
v2:
* Don't use flags but split i915_gem_shrink into locked and unlocked.
v3:
* Whitespace and checkpatch reported errors.
v4:
* Rebase.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/i915_gem_shrinker.c | 152 +++++++++++++----------
2 files changed, 84 insertions(+), 70 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d57438d87bc0..677a9af3771b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3178,7 +3178,7 @@ i915_gem_object_create_internal(struct drm_i915_private *dev_priv,
unsigned long i915_gem_shrink(struct drm_i915_private *i915,
unsigned long target,
unsigned long *nr_scanned,
- unsigned flags);
+ unsigned int flags);
#define I915_SHRINK_PURGEABLE 0x1
#define I915_SHRINK_UNBOUND 0x2
#define I915_SHRINK_BOUND 0x4
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 72d6ea0cac7e..ce539d38461c 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -115,36 +115,11 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
return !i915_gem_object_has_pages(obj);
}
-/**
- * i915_gem_shrink - Shrink buffer object caches
- * @i915: i915 device
- * @target: amount of memory to make available, in pages
- * @nr_scanned: optional output for number of pages scanned (incremental)
- * @flags: control flags for selecting cache types
- *
- * This function is the main interface to the shrinker. It will try to release
- * up to @target pages of main memory backing storage from buffer objects.
- * Selection of the specific caches can be done with @flags. This is e.g. useful
- * when purgeable objects should be removed from caches preferentially.
- *
- * Note that it's not guaranteed that released amount is actually available as
- * free system memory - the pages might still be in-used to due to other reasons
- * (like cpu mmaps) or the mm core has reused them before we could grab them.
- * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
- * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
- *
- * Also note that any kind of pinning (both per-vma address space pins and
- * backing storage pins at the buffer object level) result in the shrinker code
- * having to skip the object.
- *
- * Returns:
- * The number of pages of backing storage actually released.
- */
-unsigned long
-i915_gem_shrink(struct drm_i915_private *i915,
- unsigned long target,
- unsigned long *nr_scanned,
- unsigned flags)
+static unsigned long
+__i915_gem_shrink(struct drm_i915_private *i915,
+ unsigned long target,
+ unsigned long *nr_scanned,
+ unsigned int flags)
{
const struct {
struct list_head *list;
@@ -156,10 +131,8 @@ i915_gem_shrink(struct drm_i915_private *i915,
}, *phase;
unsigned long count = 0;
unsigned long scanned = 0;
- bool unlock;
- if (!shrinker_lock(i915, flags, &unlock))
- return 0;
+ lockdep_assert_held(&i915->drm.struct_mutex);
/*
* When shrinking the active list, also consider active contexts.
@@ -175,18 +148,8 @@ i915_gem_shrink(struct drm_i915_private *i915,
I915_WAIT_LOCKED,
MAX_SCHEDULE_TIMEOUT);
- trace_i915_gem_shrink(i915, target, flags);
i915_retire_requests(i915);
- /*
- * Unbinding of objects will require HW access; Let us not wake the
- * device just to recover a little memory. If absolutely necessary,
- * we will force the wake during oom-notifier.
- */
- if ((flags & I915_SHRINK_BOUND) &&
- !intel_runtime_pm_get_if_in_use(i915))
- flags &= ~I915_SHRINK_BOUND;
-
/*
* As we may completely rewrite the (un)bound list whilst unbinding
* (due to retiring requests) we have to strictly process only
@@ -265,15 +228,70 @@ i915_gem_shrink(struct drm_i915_private *i915,
spin_unlock(&i915->mm.obj_lock);
}
- if (flags & I915_SHRINK_BOUND)
- intel_runtime_pm_put(i915);
-
i915_retire_requests(i915);
- shrinker_unlock(i915, unlock);
-
if (nr_scanned)
*nr_scanned += scanned;
+
+ return count;
+}
+
+/**
+ * i915_gem_shrink - Shrink buffer object caches
+ * @i915: i915 device
+ * @target: amount of memory to make available, in pages
+ * @nr_scanned: optional output for number of pages scanned (incremental)
+ * @flags: control flags for selecting cache types
+ *
+ * This function is the main interface to the shrinker. It will try to release
+ * up to @target pages of main memory backing storage from buffer objects.
+ * Selection of the specific caches can be done with @flags. This is e.g. useful
+ * when purgeable objects should be removed from caches preferentially.
+ *
+ * Note that it's not guaranteed that released amount is actually available as
+ * free system memory - the pages might still be in-used to due to other reasons
+ * (like cpu mmaps) or the mm core has reused them before we could grab them.
+ * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
+ * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
+ *
+ * Also note that any kind of pinning (both per-vma address space pins and
+ * backing storage pins at the buffer object level) result in the shrinker code
+ * having to skip the object.
+ *
+ * Returns:
+ * The number of pages of backing storage actually released.
+ */
+unsigned long
+i915_gem_shrink(struct drm_i915_private *i915,
+ unsigned long target,
+ unsigned long *nr_scanned,
+ unsigned int flags)
+{
+ unsigned long count = 0;
+ bool unlock;
+
+ trace_i915_gem_shrink(i915, target, flags);
+
+ /*
+ * Unbinding of objects will require HW access; Let us not wake the
+ * device just to recover a little memory. If absolutely necessary,
+ * we will force the wake during oom-notifier.
+ */
+ if ((flags & I915_SHRINK_BOUND) &&
+ !intel_runtime_pm_get_if_in_use(i915))
+ flags &= ~I915_SHRINK_BOUND;
+
+ if (!shrinker_lock(i915, flags, &unlock))
+ goto out;
+
+ count = __i915_gem_shrink(i915, target, nr_scanned, flags);
+
+ shrinker_unlock(i915, unlock);
+
+out:
+ if (flags & I915_SHRINK_BOUND)
+ intel_runtime_pm_put(i915);
+
return count;
}
@@ -350,6 +368,7 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
{
struct drm_i915_private *i915 =
container_of(shrinker, struct drm_i915_private, mm.shrinker);
+ const unsigned int flags = I915_SHRINK_BOUND | I915_SHRINK_UNBOUND;
unsigned long freed;
bool unlock;
@@ -358,26 +377,21 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
if (!shrinker_lock(i915, 0, &unlock))
return SHRINK_STOP;
- freed = i915_gem_shrink(i915,
- sc->nr_to_scan,
- &sc->nr_scanned,
- I915_SHRINK_BOUND |
- I915_SHRINK_UNBOUND |
- I915_SHRINK_PURGEABLE);
+ freed = __i915_gem_shrink(i915,
+ sc->nr_to_scan,
+ &sc->nr_scanned,
+ flags | I915_SHRINK_PURGEABLE);
if (sc->nr_scanned < sc->nr_to_scan)
- freed += i915_gem_shrink(i915,
- sc->nr_to_scan - sc->nr_scanned,
- &sc->nr_scanned,
- I915_SHRINK_BOUND |
- I915_SHRINK_UNBOUND);
+ freed += __i915_gem_shrink(i915,
+ sc->nr_to_scan - sc->nr_scanned,
+ &sc->nr_scanned,
+ flags);
if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
intel_runtime_pm_get(i915);
- freed += i915_gem_shrink(i915,
- sc->nr_to_scan - sc->nr_scanned,
- &sc->nr_scanned,
- I915_SHRINK_ACTIVE |
- I915_SHRINK_BOUND |
- I915_SHRINK_UNBOUND);
+ freed += __i915_gem_shrink(i915,
+ sc->nr_to_scan - sc->nr_scanned,
+ &sc->nr_scanned,
+ flags | I915_SHRINK_ACTIVE);
intel_runtime_pm_put(i915);
}
@@ -475,10 +489,10 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
goto out;
intel_runtime_pm_get(i915);
- freed_pages += i915_gem_shrink(i915, -1UL, NULL,
- I915_SHRINK_BOUND |
- I915_SHRINK_UNBOUND |
- I915_SHRINK_VMAPS);
+ freed_pages += __i915_gem_shrink(i915, -1UL, NULL,
+ I915_SHRINK_BOUND |
+ I915_SHRINK_UNBOUND |
+ I915_SHRINK_VMAPS);
intel_runtime_pm_put(i915);
/* We also want to clear any cached iomaps as they wrap vmap */
--
2.19.1
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