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drm/i915: Shrink the GEM kmem_caches upon idling

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When we finally decide the gpu is idle, that is a good time to shrink
our kmem_caches.

v3: Defer until an rcu grace period after we idle.
v4: Think about epoch wraparound and how likely that is.
v5: Use I915_EPOCH_INVALID magic.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180124113608.14909-2-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2018-01-24 11:36:08 +00:00
parent 6f56103d7e
commit 84a1074920
1 changed files with 79 additions and 0 deletions
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79
drivers/gpu/drm/i915/i915_gem.c
View file

@ -3334,6 +3334,65 @@ i915_gem_retire_work_handler(struct work_struct *work)
}
}
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.
*/
kmem_cache_shrink(i915->priorities);
kmem_cache_shrink(i915->dependencies);
kmem_cache_shrink(i915->requests);
kmem_cache_shrink(i915->luts);
kmem_cache_shrink(i915->vmas);
kmem_cache_shrink(i915->objects);
}
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;
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)
{
@ -3346,6 +3405,7 @@ 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;
ktime_t end;
@ -3405,6 +3465,8 @@ i915_gem_idle_work_handler(struct work_struct *work)
GEM_BUG_ON(!dev_priv->gt.awake);
dev_priv->gt.awake = false;
epoch = dev_priv->gt.epoch;
GEM_BUG_ON(epoch == I915_EPOCH_INVALID);
rearm_hangcheck = false;
if (INTEL_GEN(dev_priv) >= 6)
@ -3421,6 +3483,23 @@ 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) {
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)