Re: [PATCH 02/11] drm/ttm: fix busy memory to fail other user v8

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 15.05.19 um 10:45 schrieb Daniel Vetter:
> On Wed, May 15, 2019 at 10:38:28AM +0200, Daniel Vetter wrote:
> > On Tue, May 14, 2019 at 02:31:18PM +0200, Christian König wrote:
> > > From: Chunming Zhou <david1.zhou@xxxxxxx>
> > >
> > > 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.
> > > v7: pass request bo->resv to ttm_bo_evict_first
> > > v8 (chk): minimal coding style fix
> > >
> > > Change-Id: I21423fb922f885465f13833c41df1e134364a8e7
> > > Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>
> > > Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> > I think this closes a big gap between ttm and the bkl/struct_mutex
> > drivers - it's much easier to guarantee you can evict everything if
> > there's only a single lock :-)
> >
> > Would be absolutely awesome if we could extract this as some kind of
> > building block, like we've done with lots of other ttm concepts already
> > (reservation_obj, fences, ...).
> >
> > Just an aside really.
> Ofc this is meant as a comment on the entire patch series, without all the
> other patches to make sure BO always stay on a relevant LRU there's still
> gaps in the guaranteed forward progress eviction algorithm.

Yeah, the problem surfaced because of patch #4. Previously TTM would 
have just ignored all errors and continued to try different placements 
and only return -ENOMEM when we ran out of a possible placements.

I probably need to either fix patch #4 or reorder the patches.

Thanks for the note,
Christian.

> -Daniel
>
> > -Daniel
> >
> > > ---
> > >   drivers/gpu/drm/ttm/ttm_bo.c | 113 +++++++++++++++++++++++++++++------
> > >   1 file changed, 96 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > > index 2845fceb2fbd..e634d3a36923 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 +781,46 @@ 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)) {
> > > +				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 +831,69 @@ 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 reservation_object *request_resv)
> > > +{
> > > +	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 ww_acquire_ctx *acquire_ctx = request_resv->lock.ctx;
> > > +		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 || !request_resv || !request_resv->lock.ctx) {
> > > +			if (first_bo)
> > > +				ttm_bo_put(first_bo);
> > > +			return -EBUSY;
> > > +		}
> > > +		if (first_bo->resv == request_resv) {
> > > +			ttm_bo_put(first_bo);
> > > +			return -EBUSY;
> > > +		}
> > > +		if (ctx->interruptible)
> > > +			ret = ww_mutex_lock_interruptible(&first_bo->resv->lock,
> > > +							  acquire_ctx);
> > > +		else
> > > +			ret = ww_mutex_lock(&first_bo->resv->lock,
> > > +					    acquire_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 +902,15 @@ 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) {
> > > @@ -907,7 +984,7 @@ 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, ctx, bo->resv);
> > >   		if (unlikely(ret != 0))
> > >   			return ret;
> > >   	} while (1);
> > > @@ -1401,7 +1478,8 @@ static int ttm_bo_force_list_clean(struct ttm_bo_device *bdev,
> > >   	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> > >   		while (!list_empty(&man->lru[i])) {
> > >   			spin_unlock(&glob->lru_lock);
> > > -			ret = ttm_mem_evict_first(bdev, mem_type, NULL, &ctx);
> > > +			ret = ttm_mem_evict_first(bdev, mem_type, NULL, &ctx,
> > > +						  NULL);
> > >   			if (ret)
> > >   				return ret;
> > >   			spin_lock(&glob->lru_lock);
> > > @@ -1772,7 +1850,8 @@ 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;
> > >   			}
> > > --
> > > 2.17.1
> > >
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

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