[PATCH 1/2] drm/ttm: fix busy memory to fail other user v6
Koenig, Christian
Christian.Koenig at amd.com
Tue May 7 11:13:48 UTC 2019
Am 07.05.19 um 13:08 schrieb zhoucm1:
>
>
> 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 at 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?
Well only if ctx->resv is NULL, otherwise we would overwrite some
reservation context given by the driver.
Probably better to give the acquir_ctx as separate parameter to
ttm_mem_evict_first().
Christian.
>
> -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;
>>> }
>
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