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

On 2019年05月07日 18:53, Koenig, Christian wrote:

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.

Prike said he see ctx->resv is null, in that case, code doesn't run into busy path. Oh, as you mentioned here, we need add .resv=bo->resv for every ttm_operation_ctx. That's a huge change which will cross all vendor drivers.

Can we just force to evaluate evict_ctx->resv = bo->resv? That means we just add one extra line: evict_ctx->resv = bo->resv. How about that?

-David

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;
  	}