[PATCH 02/11] drm/ttm: fix busy memory to fail other user v8
Christian König
ckoenig.leichtzumerken at gmail.com
Wed May 15 09:27:25 UTC 2019
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 at amd.com>
>>>
>>> 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 at amd.com>
>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>> 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 at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch
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