[PATCH 4/6] drm/ttm: rework BO delayed delete.
Pan, Xinhui
Xinhui.Pan at amd.com
Tue Feb 11 05:43:30 UTC 2020
comments inline
> 2020年2月11日 13:26，Pan, Xinhui <Xinhui.Pan at amd.com> 写道：
>
> comments inline.
> [xh]
>
>
>> 2020年2月10日 23:09，Christian König <ckoenig.leichtzumerken at gmail.com> 写道：
>>
>> This patch reworks the whole delayed deletion of BOs which aren't idle.
>>
>> Instead of having two counters for the BO structure we resurrect the BO
>> when we find that a deleted BO is not idle yet.
>>
>> This has many advantages, especially that we don't need to
>> increment/decrement the BOs reference counter any more when it
>> moves on the LRUs.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>> drivers/gpu/drm/ttm/ttm_bo.c | 217 +++++++++++++-----------------
>> drivers/gpu/drm/ttm/ttm_bo_util.c | 1 -
>> include/drm/ttm/ttm_bo_api.h | 11 +-
>> 3 files changed, 97 insertions(+), 132 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index e12fc2c2d165..d0624685f5d2 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -145,26 +145,6 @@ static inline uint32_t ttm_bo_type_flags(unsigned type)
>> return 1 << (type);
>> }
>>
>> -static void ttm_bo_release_list(struct kref *list_kref)
>> -{
>> - struct ttm_buffer_object *bo =
>> - container_of(list_kref, struct ttm_buffer_object, list_kref);
>> - size_t acc_size = bo->acc_size;
>> -
>> - BUG_ON(kref_read(&bo->list_kref));
>> - BUG_ON(kref_read(&bo->kref));
>> - BUG_ON(bo->mem.mm_node != NULL);
>> - BUG_ON(!list_empty(&bo->lru));
>> - BUG_ON(!list_empty(&bo->ddestroy));
>> - ttm_tt_destroy(bo->ttm);
>> - atomic_dec(&ttm_bo_glob.bo_count);
>> - dma_fence_put(bo->moving);
>> - if (!ttm_bo_uses_embedded_gem_object(bo))
>> - dma_resv_fini(&bo->base._resv);
>> - bo->destroy(bo);
>> - ttm_mem_global_free(&ttm_mem_glob, acc_size);
>> -}
>> -
>> static void ttm_bo_add_mem_to_lru(struct ttm_buffer_object *bo,
>> struct ttm_mem_reg *mem)
>> {
>> @@ -181,21 +161,14 @@ static void ttm_bo_add_mem_to_lru(struct ttm_buffer_object *bo,
>>
>> man = &bdev->man[mem->mem_type];
>> list_add_tail(&bo->lru, &man->lru[bo->priority]);
>> - kref_get(&bo->list_kref);
>>
>> if (!(man->flags & TTM_MEMTYPE_FLAG_FIXED) && bo->ttm &&
>> !(bo->ttm->page_flags & (TTM_PAGE_FLAG_SG |
>> TTM_PAGE_FLAG_SWAPPED))) {
>> list_add_tail(&bo->swap, &ttm_bo_glob.swap_lru[bo->priority]);
>> - kref_get(&bo->list_kref);
>> }
>> }
>>
>> -static void ttm_bo_ref_bug(struct kref *list_kref)
>> -{
>> - BUG();
>> -}
>> -
>> static void ttm_bo_del_from_lru(struct ttm_buffer_object *bo)
>> {
>> struct ttm_bo_device *bdev = bo->bdev;
>> @@ -203,12 +176,10 @@ static void ttm_bo_del_from_lru(struct ttm_buffer_object *bo)
>>
>> if (!list_empty(&bo->swap)) {
>> list_del_init(&bo->swap);
>> - kref_put(&bo->list_kref, ttm_bo_ref_bug);
>> notify = true;
>> }
>> if (!list_empty(&bo->lru)) {
>> list_del_init(&bo->lru);
>> - kref_put(&bo->list_kref, ttm_bo_ref_bug);
>> notify = true;
>> }
>>
>> @@ -421,8 +392,7 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
>> BUG_ON(!dma_resv_trylock(&bo->base._resv));
>>
>> r = dma_resv_copy_fences(&bo->base._resv, bo->base.resv);
>> - if (r)
>> - dma_resv_unlock(&bo->base._resv);
>> + dma_resv_unlock(&bo->base._resv);
>>
>> return r;
>> }
>> @@ -449,68 +419,10 @@ static void ttm_bo_flush_all_fences(struct ttm_buffer_object *bo)
>> rcu_read_unlock();
>> }
>>
>> -static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
>> -{
>> - struct ttm_bo_device *bdev = bo->bdev;
>> - int ret;
>> -
>> - ret = ttm_bo_individualize_resv(bo);
>> - if (ret) {
>> - /* Last resort, if we fail to allocate memory for the
>> - * fences block for the BO to become idle
>> - */
>> - dma_resv_wait_timeout_rcu(bo->base.resv, true, false,
>> - 30 * HZ);
>> - spin_lock(&ttm_bo_glob.lru_lock);
>> - goto error;
>> - }
>> -
>> - spin_lock(&ttm_bo_glob.lru_lock);
>> - ret = dma_resv_trylock(bo->base.resv) ? 0 : -EBUSY;
>> - if (!ret) {
>> - if (dma_resv_test_signaled_rcu(&bo->base._resv, true)) {
>> - ttm_bo_del_from_lru(bo);
>> - spin_unlock(&ttm_bo_glob.lru_lock);
>> - if (bo->base.resv != &bo->base._resv)
>> - dma_resv_unlock(&bo->base._resv);
>> -
>> - ttm_bo_cleanup_memtype_use(bo);
>> - dma_resv_unlock(bo->base.resv);
>> - return;
>> - }
>> -
>> - ttm_bo_flush_all_fences(bo);
>> -
>> - /*
>> - * Make NO_EVICT bos immediately available to
>> - * shrinkers, now that they are queued for
>> - * destruction.
>> - */
>> - if (bo->mem.placement & TTM_PL_FLAG_NO_EVICT) {
>> - bo->mem.placement &= ~TTM_PL_FLAG_NO_EVICT;
>> - ttm_bo_move_to_lru_tail(bo, NULL);
>> - }
>> -
>> - dma_resv_unlock(bo->base.resv);
>> - }
>> - if (bo->base.resv != &bo->base._resv) {
>> - ttm_bo_flush_all_fences(bo);
>> - dma_resv_unlock(&bo->base._resv);
>> - }
>> -
>> -error:
>> - kref_get(&bo->list_kref);
>> - list_add_tail(&bo->ddestroy, &bdev->ddestroy);
>> - spin_unlock(&ttm_bo_glob.lru_lock);
>> -
>> - schedule_delayed_work(&bdev->wq,
>> - ((HZ / 100) < 1) ? 1 : HZ / 100);
>> -}
>> -
>> /**
>> * function ttm_bo_cleanup_refs
>> - * If bo idle, remove from delayed- and lru lists, and unref.
>> - * If not idle, do nothing.
>> + * If bo idle, remove from lru lists, and unref.
>> + * If not idle, block if possible.
>> *
>> * Must be called with lru_lock and reservation held, this function
>> * will drop the lru lock and optionally the reservation lock before returning.
>> @@ -572,14 +484,14 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
>>
>> ttm_bo_del_from_lru(bo);
>> list_del_init(&bo->ddestroy);
>> - kref_put(&bo->list_kref, ttm_bo_ref_bug);
>> -
>> spin_unlock(&ttm_bo_glob.lru_lock);
>> ttm_bo_cleanup_memtype_use(bo);
>>
>> if (unlock_resv)
>> dma_resv_unlock(bo->base.resv);
>>
>> + ttm_bo_put(bo);
>> +
>> return 0;
>> }
>>
>> @@ -601,8 +513,9 @@ static bool ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
>>
>> bo = list_first_entry(&bdev->ddestroy, struct ttm_buffer_object,
>> ddestroy);
>> - kref_get(&bo->list_kref);
>> list_move_tail(&bo->ddestroy, &removed);
>> + if (!ttm_bo_get_unless_zero(bo))
>> + continue;
>>
>> if (remove_all || bo->base.resv != &bo->base._resv) {
>> spin_unlock(&glob->lru_lock);
>> @@ -617,7 +530,7 @@ static bool ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
>> spin_unlock(&glob->lru_lock);
>> }
>>
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(bo);
>> spin_lock(&glob->lru_lock);
>> }
>> list_splice_tail(&removed, &bdev->ddestroy);
>> @@ -643,16 +556,68 @@ static void ttm_bo_release(struct kref *kref)
>> container_of(kref, struct ttm_buffer_object, kref);
>> struct ttm_bo_device *bdev = bo->bdev;
>> struct ttm_mem_type_manager *man = &bdev->man[bo->mem.mem_type];
>> + size_t acc_size = bo->acc_size;
>> + int ret;
>>
>> - if (bo->bdev->driver->release_notify)
>> - bo->bdev->driver->release_notify(bo);
>> + if (!bo->deleted) {
>> + if (bo->bdev->driver->release_notify)
>> + bo->bdev->driver->release_notify(bo);
>>
>> - drm_vma_offset_remove(bdev->vma_manager, &bo->base.vma_node);
>> - ttm_mem_io_lock(man, false);
>> - ttm_mem_io_free_vm(bo);
>> - ttm_mem_io_unlock(man);
>> - ttm_bo_cleanup_refs_or_queue(bo);
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + drm_vma_offset_remove(bdev->vma_manager, &bo->base.vma_node);
>> + ttm_mem_io_lock(man, false);
>> + ttm_mem_io_free_vm(bo);
>> + ttm_mem_io_unlock(man);
>> +
>> + ret = ttm_bo_individualize_resv(bo);
>> + if (ret) {
>> + /* Last resort, if we fail to allocate memory for the
>> + * fences block for the BO to become idle
>> + */
>> + dma_resv_wait_timeout_rcu(bo->base.resv, true, false,
>> + 30 * HZ);
>> + }
>> + }
>> +
>> + if (!dma_resv_test_signaled_rcu(bo->base.resv, true)) {
>> + /* The BO is not idle, resurrect it for delayed destroy */
>> + ttm_bo_flush_all_fences(bo);
>> + bo->deleted = true;
>> +
>> + /*
>> + * Make NO_EVICT bos immediately available to
>> + * shrinkers, now that they are queued for
>> + * destruction.
>> + */
>> + if (bo->mem.placement & TTM_PL_FLAG_NO_EVICT) {
>> + bo->mem.placement &= ~TTM_PL_FLAG_NO_EVICT;
>> + ttm_bo_move_to_lru_tail(bo, NULL);
>
> [xh] this should be under lru lock.
>
>> + }
>> +
>> + spin_lock(&ttm_bo_glob.lru_lock);
>> + kref_init(&bo->kref);
>> + list_add_tail(&bo->ddestroy, &bdev->ddestroy);
>> + spin_unlock(&ttm_bo_glob.lru_lock);
>> +
>> + schedule_delayed_work(&bdev->wq,
>> + ((HZ / 100) < 1) ? 1 : HZ / 100);
>> + return;
>> + }
>> +
>> + spin_lock(&ttm_bo_glob.lru_lock);
>> + ttm_bo_del_from_lru(bo);
>> + list_del(&bo->ddestroy);
>> + spin_unlock(&ttm_bo_glob.lru_lock);
>> +
>> + ttm_bo_cleanup_memtype_use(bo);
>> +
>> + BUG_ON(bo->mem.mm_node != NULL);
>> + ttm_tt_destroy(bo->ttm);
>
> [xh] already destroy it in ttm_bo_cleanup_memtype_use.
>
>
>> + atomic_dec(&ttm_bo_glob.bo_count);
>> + dma_fence_put(bo->moving);
>> + if (!ttm_bo_uses_embedded_gem_object(bo))
>> + dma_resv_fini(&bo->base._resv);
>> + bo->destroy(bo);
>> + ttm_mem_global_free(&ttm_mem_glob, acc_size);
>> }
>>
>> void ttm_bo_put(struct ttm_buffer_object *bo)
>> @@ -755,8 +720,7 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
>>
>> if (bo->base.resv == ctx->resv) {
>> dma_resv_assert_held(bo->base.resv);
>> - if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT
>> - || !list_empty(&bo->ddestroy))
>> + if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT || bo->deleted)
>> ret = true;
>> *locked = false;
>> if (busy)
>> @@ -837,6 +801,11 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>> dma_resv_unlock(bo->base.resv);
>> continue;
>> }
>> + if (!ttm_bo_get_unless_zero(bo)) {
>> + if (locked)
>> + dma_resv_unlock(bo->base.resv);
>> + continue;
>> + }
>> break;
>> }
>>
>> @@ -848,21 +817,19 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>> }
>>
>> if (!bo) {
>> - if (busy_bo)
>> - kref_get(&busy_bo->list_kref);
>> + if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
>> + busy_bo = NULL;
>> spin_unlock(&ttm_bo_glob.lru_lock);
>> ret = ttm_mem_evict_wait_busy(busy_bo, ctx, ticket);
>> if (busy_bo)
>> - kref_put(&busy_bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(busy_bo);
>> return ret;
>> }
>>
>> - kref_get(&bo->list_kref);
>> -
>> - if (!list_empty(&bo->ddestroy)) {
>> + if (bo->deleted) {
>> ret = ttm_bo_cleanup_refs(bo, ctx->interruptible,
>> ctx->no_wait_gpu, locked);
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(bo);
>> return ret;
>> }
>>
>> @@ -872,7 +839,7 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>> if (locked)
>> ttm_bo_unreserve(bo);
>>
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(bo);
>> return ret;
>> }
>>
>> @@ -1284,7 +1251,6 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
>> bo->destroy = destroy ? destroy : ttm_bo_default_destroy;
>>
>> kref_init(&bo->kref);
>> - kref_init(&bo->list_kref);
>> INIT_LIST_HEAD(&bo->lru);
>> INIT_LIST_HEAD(&bo->ddestroy);
>> INIT_LIST_HEAD(&bo->swap);
>> @@ -1804,11 +1770,18 @@ int ttm_bo_swapout(struct ttm_bo_global *glob, struct ttm_operation_ctx *ctx)
>> spin_lock(&glob->lru_lock);
>> for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>> list_for_each_entry(bo, &glob->swap_lru[i], swap) {
>> - if (ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
>> - NULL)) {
>> - ret = 0;
>> - break;
>> + if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
>> + NULL))
>> + continue;
>> +
>> + if (!ttm_bo_get_unless_zero(bo)) {
>> + if (locked)
>> + dma_resv_unlock(bo->base.resv);
>> + continue;
>> }
>
> [xh] As you get the bo. when you put it?
>
> You only put one bo just before return. BUT you get the bos in the for loop. Am I missing somethings?
>
> thanks
> xinhui
>
>
[xh] Never mind.
I missed the break;
thanks
xinhui
>> +
>> + ret = 0;
>> + break;
>> }
>> if (!ret)
>> break;
>> @@ -1819,11 +1792,9 @@ int ttm_bo_swapout(struct ttm_bo_global *glob, struct ttm_operation_ctx *ctx)
>> return ret;
>> }
>>
>> - kref_get(&bo->list_kref);
>> -
>> - if (!list_empty(&bo->ddestroy)) {
>> + if (bo->deleted) {
>> ret = ttm_bo_cleanup_refs(bo, false, false, locked);
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(bo);
>> return ret;
>> }
>>
>> @@ -1877,7 +1848,7 @@ int ttm_bo_swapout(struct ttm_bo_global *glob, struct ttm_operation_ctx *ctx)
>> */
>> if (locked)
>> dma_resv_unlock(bo->base.resv);
>> - kref_put(&bo->list_kref, ttm_bo_release_list);
>> + ttm_bo_put(bo);
>> return ret;
>> }
>> EXPORT_SYMBOL(ttm_bo_swapout);
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> index 86d152472f38..c8e359ded1df 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> @@ -507,7 +507,6 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
>> fbo->base.moving = NULL;
>> drm_vma_node_reset(&fbo->base.base.vma_node);
>>
>> - kref_init(&fbo->base.list_kref);
>> kref_init(&fbo->base.kref);
>> fbo->base.destroy = &ttm_transfered_destroy;
>> fbo->base.acc_size = 0;
>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>> index 66ca49db9633..b9bc1b00142e 100644
>> --- a/include/drm/ttm/ttm_bo_api.h
>> +++ b/include/drm/ttm/ttm_bo_api.h
>> @@ -135,18 +135,14 @@ struct ttm_tt;
>> * @num_pages: Actual number of pages.
>> * @acc_size: Accounted size for this object.
>> * @kref: Reference count of this buffer object. When this refcount reaches
>> - * zero, the object is put on the delayed delete list.
>> - * @list_kref: List reference count of this buffer object. This member is
>> - * used to avoid destruction while the buffer object is still on a list.
>> - * Lru lists may keep one refcount, the delayed delete list, and kref != 0
>> - * keeps one refcount. When this refcount reaches zero,
>> - * the object is destroyed.
>> + * zero, the object is destroyed or put on the delayed delete list.
>> * @mem: structure describing current placement.
>> * @persistent_swap_storage: Usually the swap storage is deleted for buffers
>> * pinned in physical memory. If this behaviour is not desired, this member
>> * holds a pointer to a persistent shmem object.
>> * @ttm: TTM structure holding system pages.
>> * @evicted: Whether the object was evicted without user-space knowing.
>> + * @deleted: True if the object is only a zombie and already deleted.
>> * @lru: List head for the lru list.
>> * @ddestroy: List head for the delayed destroy list.
>> * @swap: List head for swap LRU list.
>> @@ -183,9 +179,7 @@ struct ttm_buffer_object {
>> /**
>> * Members not needing protection.
>> */
>> -
>> struct kref kref;
>> - struct kref list_kref;
>>
>> /**
>> * Members protected by the bo::resv::reserved lock.
>> @@ -195,6 +189,7 @@ struct ttm_buffer_object {
>> struct file *persistent_swap_storage;
>> struct ttm_tt *ttm;
>> bool evicted;
>> + bool deleted;
>>
>> /**
>> * Members protected by the bdev::lru_lock.
>> --
>> 2.17.1
>>
>
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