Re: [PATCH 1/2] drm/ttm: fix busy memory to fail other user v6

["Koenig, Christian" <Christian.Koenig@amd.com>]

Am 07.05.19 um 11:36 schrieb Chunming Zhou:
> heavy gpu job could occupy memory long time, which lead other user fail to get memory.
>
> basically pick up Christian idea:
>
> 1. Reserve the BO in DC using a ww_mutex ticket (trivial).
> 2. If we then run into this EBUSY condition in TTM check if the BO we need memory for (or rather the ww_mutex of its reservation object) has a ticket assigned.
> 3. If we have a ticket we grab a reference to the first BO on the LRU, drop the LRU lock and try to grab the reservation lock with the ticket.
> 4. If getting the reservation lock with the ticket succeeded we check if the BO is still the first one on the LRU in question (the BO could have moved).
> 5. If the BO is still the first one on the LRU in question we try to evict it as we would evict any other BO.
> 6. If any of the "If's" above fail we just back off and return -EBUSY.
>
> v2: fix some minor check
> v3: address Christian v2 comments.
> v4: fix some missing
> v5: handle first_bo unlock and bo_get/put
> v6: abstract unified iterate function, and handle all possible usecase not only pinned bo.
>
> Change-Id: I21423fb922f885465f13833c41df1e134364a8e7
> Signed-off-by: Chunming Zhou <david1.zhou@amd.com>
> ---
>   drivers/gpu/drm/ttm/ttm_bo.c | 113 ++++++++++++++++++++++++++++++-----
>   1 file changed, 97 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 8502b3ed2d88..bbf1d14d00a7 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -766,11 +766,13 @@ EXPORT_SYMBOL(ttm_bo_eviction_valuable);
>    * b. Otherwise, trylock it.
>    */
>   static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
> -			struct ttm_operation_ctx *ctx, bool *locked)
> +			struct ttm_operation_ctx *ctx, bool *locked, bool *busy)
>   {
>   	bool ret = false;
>   
>   	*locked = false;
> +	if (busy)
> +		*busy = false;
>   	if (bo->resv == ctx->resv) {
>   		reservation_object_assert_held(bo->resv);
>   		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT
> @@ -779,35 +781,45 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
>   	} else {
>   		*locked = reservation_object_trylock(bo->resv);
>   		ret = *locked;
> +		if (!ret && busy)
> +			*busy = true;
>   	}
>   
>   	return ret;
>   }
>   
> -static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> -			       uint32_t mem_type,
> -			       const struct ttm_place *place,
> -			       struct ttm_operation_ctx *ctx)
> +static struct ttm_buffer_object*
> +ttm_mem_find_evitable_bo(struct ttm_bo_device *bdev,
> +			 struct ttm_mem_type_manager *man,
> +			 const struct ttm_place *place,
> +			 struct ttm_operation_ctx *ctx,
> +			 struct ttm_buffer_object **first_bo,
> +			 bool *locked)
>   {
> -	struct ttm_bo_global *glob = bdev->glob;
> -	struct ttm_mem_type_manager *man = &bdev->man[mem_type];
>   	struct ttm_buffer_object *bo = NULL;
> -	bool locked = false;
> -	unsigned i;
> -	int ret;
> +	int i;
>   
> -	spin_lock(&glob->lru_lock);
> +	if (first_bo)
> +		*first_bo = NULL;
>   	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>   		list_for_each_entry(bo, &man->lru[i], lru) {
> -			if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked))
> +			bool busy = false;
> +			if (!ttm_bo_evict_swapout_allowable(bo, ctx, locked,
> +							    &busy)) {

A newline between declaration and code please.

> +				if (first_bo && !(*first_bo) && busy) {
> +					ttm_bo_get(bo);
> +					*first_bo = bo;
> +				}
>   				continue;
> +			}
>   
>   			if (place && !bdev->driver->eviction_valuable(bo,
>   								      place)) {
> -				if (locked)
> +				if (*locked)
>   					reservation_object_unlock(bo->resv);
>   				continue;
>   			}
> +
>   			break;
>   		}
>   
> @@ -818,9 +830,66 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>   		bo = NULL;
>   	}
>   
> +	return bo;
> +}
> +
> +static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> +			       uint32_t mem_type,
> +			       const struct ttm_place *place,
> +			       struct ttm_operation_ctx *ctx)
> +{
> +	struct ttm_bo_global *glob = bdev->glob;
> +	struct ttm_mem_type_manager *man = &bdev->man[mem_type];
> +	struct ttm_buffer_object *bo = NULL, *first_bo = NULL;
> +	bool locked = false;
> +	int ret;
> +
> +	spin_lock(&glob->lru_lock);
> +	bo = ttm_mem_find_evitable_bo(bdev, man, place, ctx, &first_bo,
> +				      &locked);
>   	if (!bo) {
> +		struct ttm_operation_ctx busy_ctx;
> +
>   		spin_unlock(&glob->lru_lock);
> -		return -EBUSY;
> +		/* check if other user occupy memory too long time */
> +		if (!first_bo || !ctx || !ctx->resv || !ctx->resv->lock.ctx) {
> +			if (first_bo)
> +				ttm_bo_put(first_bo);
> +			return -EBUSY;
> +		}
> +		if (first_bo->resv == ctx->resv) {
> +			ttm_bo_put(first_bo);
> +			return -EBUSY;
> +		}
> +		if (ctx->interruptible)
> +			ret = ww_mutex_lock_interruptible(&first_bo->resv->lock,
> +							  ctx->resv->lock.ctx);
> +		else
> +			ret = ww_mutex_lock(&first_bo->resv->lock, ctx->resv->lock.ctx);
> +		if (ret) {
> +			ttm_bo_put(first_bo);
> +			return ret;
> +		}
> +		spin_lock(&glob->lru_lock);
> +		/* previous busy resv lock is held by above, idle now,
> +		 * so let them evictable.
> +		 */
> +		busy_ctx.interruptible = ctx->interruptible;
> +		busy_ctx.no_wait_gpu   = ctx->no_wait_gpu;
> +		busy_ctx.resv	       = first_bo->resv;
> +		busy_ctx.flags	       = TTM_OPT_FLAG_ALLOW_RES_EVICT;
> +
> +		bo = ttm_mem_find_evitable_bo(bdev, man, place, &busy_ctx, NULL,
> +					      &locked);
> +		if (bo && (bo->resv == first_bo->resv))
> +			locked = true;
> +		else if (bo)
> +			ww_mutex_unlock(&first_bo->resv->lock);
> +		if (!bo) {
> +			spin_unlock(&glob->lru_lock);
> +			ttm_bo_put(first_bo);
> +			return -EBUSY;
> +		}
>   	}
>   
>   	kref_get(&bo->list_kref);
> @@ -829,11 +898,15 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>   		ret = ttm_bo_cleanup_refs(bo, ctx->interruptible,
>   					  ctx->no_wait_gpu, locked);
>   		kref_put(&bo->list_kref, ttm_bo_release_list);
> +		if (first_bo)
> +			ttm_bo_put(first_bo);
>   		return ret;
>   	}
>   
>   	ttm_bo_del_from_lru(bo);
>   	spin_unlock(&glob->lru_lock);
> +	if (first_bo)
> +		ttm_bo_put(first_bo);
>   
>   	ret = ttm_bo_evict(bo, ctx);
>   	if (locked) {
> @@ -899,6 +972,13 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
>   {
>   	struct ttm_bo_device *bdev = bo->bdev;
>   	struct ttm_mem_type_manager *man = &bdev->man[mem_type];
> +	struct ttm_operation_ctx native_ctx = {
> +		.interruptible = false,
> +		.no_wait_gpu = false,
> +		.resv = bo->resv,
> +		.flags = 0
> +	};
> +	struct ttm_operation_ctx *evict_ctx = ctx ? ctx : &native_ctx;

I thought we made the ctx parameter mandatory, didn't we? Could be that 
I remember that incorrectly.

Christian.

>   	int ret;
>   
>   	do {
> @@ -907,7 +987,7 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
>   			return ret;
>   		if (mem->mm_node)
>   			break;
> -		ret = ttm_mem_evict_first(bdev, mem_type, place, ctx);
> +		ret = ttm_mem_evict_first(bdev, mem_type, place, evict_ctx);
>   		if (unlikely(ret != 0))
>   			return ret;
>   	} while (1);
> @@ -1784,7 +1864,8 @@ 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)) {
> +			if (ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
> +							   NULL)) {
>   				ret = 0;
>   				break;
>   			}

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