Makes it possible to reserve a list of buffer objects with a single spin lock / unlock if there is no contention. Should improve cpu usage on SMP kernels.
v2: Initialize private list members on reserve and don't call ttm_bo_list_ref_sub() with zero put_count.
Signed-off-by: Thomas Hellstrom thellstrom@vmware.com --- drivers/gpu/drm/ttm/ttm_bo.c | 32 ++++---- drivers/gpu/drm/ttm/ttm_execbuf_util.c | 124 +++++++++++++++++++++++++++++--- include/drm/ttm/ttm_bo_api.h | 38 ++++++++++ include/drm/ttm/ttm_bo_driver.h | 14 ++++ include/drm/ttm/ttm_execbuf_util.h | 6 ++- 5 files changed, 186 insertions(+), 28 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 148a322..a586378 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -169,7 +169,7 @@ int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo, bool interruptible) } EXPORT_SYMBOL(ttm_bo_wait_unreserved);
-static void ttm_bo_add_to_lru(struct ttm_buffer_object *bo) +void ttm_bo_add_to_lru(struct ttm_buffer_object *bo) { struct ttm_bo_device *bdev = bo->bdev; struct ttm_mem_type_manager *man; @@ -191,11 +191,7 @@ static void ttm_bo_add_to_lru(struct ttm_buffer_object *bo) } }
-/** - * Call with the lru_lock held. - */ - -static int ttm_bo_del_from_lru(struct ttm_buffer_object *bo) +int ttm_bo_del_from_lru(struct ttm_buffer_object *bo) { int put_count = 0;
@@ -267,6 +263,15 @@ static void ttm_bo_ref_bug(struct kref *list_kref) BUG(); }
+void ttm_bo_list_ref_sub(struct ttm_buffer_object *bo, int count, + bool never_free) +{ + while (count--) + kref_put(&bo->list_kref, + (never_free || (count >= 0)) ? ttm_bo_ref_bug : + ttm_bo_release_list); +} + int ttm_bo_reserve(struct ttm_buffer_object *bo, bool interruptible, bool no_wait, bool use_sequence, uint32_t sequence) @@ -282,8 +287,7 @@ int ttm_bo_reserve(struct ttm_buffer_object *bo, put_count = ttm_bo_del_from_lru(bo); spin_unlock(&glob->lru_lock);
- while (put_count--) - kref_put(&bo->list_kref, ttm_bo_ref_bug); + ttm_bo_list_ref_sub(bo, put_count, true);
return ret; } @@ -496,8 +500,7 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo) spin_unlock(&glob->lru_lock); ttm_bo_cleanup_memtype_use(bo);
- while (put_count--) - kref_put(&bo->list_kref, ttm_bo_ref_bug); + ttm_bo_list_ref_sub(bo, put_count, true);
return; } else { @@ -580,8 +583,7 @@ retry: spin_unlock(&glob->lru_lock); ttm_bo_cleanup_memtype_use(bo);
- while (put_count--) - kref_put(&bo->list_kref, ttm_bo_ref_bug); + ttm_bo_list_ref_sub(bo, put_count, true);
return 0; } @@ -802,8 +804,7 @@ retry:
BUG_ON(ret != 0);
- while (put_count--) - kref_put(&bo->list_kref, ttm_bo_ref_bug); + ttm_bo_list_ref_sub(bo, put_count, true);
ret = ttm_bo_evict(bo, interruptible, no_wait_reserve, no_wait_gpu); ttm_bo_unreserve(bo); @@ -1783,8 +1784,7 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink) put_count = ttm_bo_del_from_lru(bo); spin_unlock(&glob->lru_lock);
- while (put_count--) - kref_put(&bo->list_kref, ttm_bo_ref_bug); + ttm_bo_list_ref_sub(bo, put_count, true);
/** * Wait for GPU, then move to system cached. diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c index c285c29..201a71d 100644 --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c @@ -32,6 +32,72 @@ #include <linux/sched.h> #include <linux/module.h>
+static void ttm_eu_backoff_reservation_locked(struct list_head *list) +{ + struct ttm_validate_buffer *entry; + + list_for_each_entry(entry, list, head) { + struct ttm_buffer_object *bo = entry->bo; + if (!entry->reserved) + continue; + + if (entry->removed) { + ttm_bo_add_to_lru(bo); + entry->removed = false; + + } + entry->reserved = false; + atomic_set(&bo->reserved, 0); + wake_up_all(&bo->event_queue); + } +} + +static void ttm_eu_del_from_lru_locked(struct list_head *list) +{ + struct ttm_validate_buffer *entry; + + list_for_each_entry(entry, list, head) { + struct ttm_buffer_object *bo = entry->bo; + if (!entry->reserved) + continue; + + if (!entry->removed) { + entry->put_count = ttm_bo_del_from_lru(bo); + entry->removed = true; + } + } +} + +static void ttm_eu_list_ref_sub(struct list_head *list) +{ + struct ttm_validate_buffer *entry; + + list_for_each_entry(entry, list, head) { + struct ttm_buffer_object *bo = entry->bo; + + if (entry->put_count) { + ttm_bo_list_ref_sub(bo, entry->put_count, true); + entry->put_count = 0; + } + } +} + +static int ttm_eu_wait_unreserved_locked(struct list_head *list, + struct ttm_buffer_object *bo) +{ + struct ttm_bo_global *glob = bo->glob; + int ret; + + ttm_eu_del_from_lru_locked(list); + spin_unlock(&glob->lru_lock); + ret = ttm_bo_wait_unreserved(bo, true); + spin_lock(&glob->lru_lock); + if (unlikely(ret != 0)) + ttm_eu_backoff_reservation_locked(list); + return ret; +} + + void ttm_eu_backoff_reservation(struct list_head *list) { struct ttm_validate_buffer *entry; @@ -61,35 +127,71 @@ EXPORT_SYMBOL(ttm_eu_backoff_reservation);
int ttm_eu_reserve_buffers(struct list_head *list, uint32_t val_seq) { + struct ttm_bo_global *glob; struct ttm_validate_buffer *entry; int ret;
+ if (list_empty(list)) + return 0; + + list_for_each_entry(entry, list, head) { + entry->reserved = false; + entry->put_count = 0; + entry->removed = false; + } + + entry = list_first_entry(list, struct ttm_validate_buffer, head); + glob = entry->bo->glob; + retry: + spin_lock(&glob->lru_lock); list_for_each_entry(entry, list, head) { struct ttm_buffer_object *bo = entry->bo;
- entry->reserved = false; - ret = ttm_bo_reserve(bo, true, false, true, val_seq); - if (ret != 0) { - ttm_eu_backoff_reservation(list); - if (ret == -EAGAIN) { - ret = ttm_bo_wait_unreserved(bo, true); - if (unlikely(ret != 0)) - return ret; - goto retry; - } else +retry_this_bo: + ret = ttm_bo_reserve_locked(bo, true, true, true, val_seq); + switch (ret) { + case 0: + break; + case -EBUSY: + ret = ttm_eu_wait_unreserved_locked(list, bo); + if (unlikely(ret != 0)) { + spin_unlock(&glob->lru_lock); + ttm_eu_list_ref_sub(list); + return ret; + } + goto retry_this_bo; + case -EAGAIN: + ttm_eu_backoff_reservation_locked(list); + spin_unlock(&glob->lru_lock); + ttm_eu_list_ref_sub(list); + ret = ttm_bo_wait_unreserved(bo, true); + if (unlikely(ret != 0)) return ret; + goto retry; + default: + ttm_eu_backoff_reservation_locked(list); + spin_unlock(&glob->lru_lock); + ttm_eu_list_ref_sub(list); + return ret; }
entry->reserved = true; if (unlikely(atomic_read(&bo->cpu_writers) > 0)) { - ttm_eu_backoff_reservation(list); + ttm_eu_backoff_reservation_locked(list); + spin_unlock(&glob->lru_lock); + ttm_eu_list_ref_sub(list); ret = ttm_bo_wait_cpu(bo, false); if (ret) return ret; goto retry; } } + + ttm_eu_del_from_lru_locked(list); + spin_unlock(&glob->lru_lock); + ttm_eu_list_ref_sub(list); + return 0; } EXPORT_SYMBOL(ttm_eu_reserve_buffers); diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h index beafc15..b0fc9c1 100644 --- a/include/drm/ttm/ttm_bo_api.h +++ b/include/drm/ttm/ttm_bo_api.h @@ -364,6 +364,44 @@ extern int ttm_bo_validate(struct ttm_buffer_object *bo, */ extern void ttm_bo_unref(struct ttm_buffer_object **bo);
+ +/** + * ttm_bo_list_ref_sub + * + * @bo: The buffer object. + * @count: The number of references with which to decrease @bo::list_kref; + * @never_free: The refcount should not reach zero with this operation. + * + * Release @count lru list references to this buffer object. + */ +extern void ttm_bo_list_ref_sub(struct ttm_buffer_object *bo, int count, + bool never_free); + +/** + * ttm_bo_add_to_lru + * + * @bo: The buffer object. + * + * Add this bo to the relevant mem type lru and, if it's backed by + * system pages (ttms) to the swap list. + * This function must be called with struct ttm_bo_global::lru_lock held, and + * is typically called immediately prior to unreserving a bo. + */ +extern void ttm_bo_add_to_lru(struct ttm_buffer_object *bo); + +/** + * ttm_bo_del_from_lru + * + * @bo: The buffer object. + * + * Remove this bo from all lru lists used to lookup and reserve an object. + * This function must be called with struct ttm_bo_global::lru_lock held, + * and is usually called just immediately after the bo has been reserved to + * avoid recursive reservation from lru lists. + */ +extern int ttm_bo_del_from_lru(struct ttm_buffer_object *bo); + + /** * ttm_bo_lock_delayed_workqueue * diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h index 8e0c848..95068e6 100644 --- a/include/drm/ttm/ttm_bo_driver.h +++ b/include/drm/ttm/ttm_bo_driver.h @@ -864,6 +864,20 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo, bool interruptible, bool no_wait, bool use_sequence, uint32_t sequence);
+ +/** + * ttm_bo_reserve_locked: + * + * Similar to ttm_bo_reserve, but must be called with the glob::lru_lock + * spinlock held, and will not remove reserved buffers from the lru lists. + * The function may release the LRU spinlock if it needs to sleep. + */ + +extern int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, + bool interruptible, + bool no_wait, bool use_sequence, + uint32_t sequence); + /** * ttm_bo_unreserve * diff --git a/include/drm/ttm/ttm_execbuf_util.h b/include/drm/ttm/ttm_execbuf_util.h index cd2c475..fd09b84 100644 --- a/include/drm/ttm/ttm_execbuf_util.h +++ b/include/drm/ttm/ttm_execbuf_util.h @@ -41,7 +41,9 @@ * @bo: refcounted buffer object pointer. * @new_sync_obj_arg: New sync_obj_arg for @bo, to be used once * adding a new sync object. - * @reservied: Indicates whether @bo has been reserved for validation. + * @reserved: Indicates whether @bo has been reserved for validation. + * @removed: Indicates whether @bo has been removed from lru lists. + * @put_count: Number of outstanding references on bo::list_kref. */
struct ttm_validate_buffer { @@ -49,6 +51,8 @@ struct ttm_validate_buffer { struct ttm_buffer_object *bo; void *new_sync_obj_arg; bool reserved; + bool removed; + int put_count; };
/**