[PATCH 1/2] drm/ttm: fix busy memory to fail other user v6
zhoucm1
zhoucm1 at amd.com
Tue May 7 11:22:17 UTC 2019
On 2019年05月07日 19:13, Koenig, Christian wrote:
> 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().
still put acquire_ctx into ttm_operation_ctx? Then that's same ctx->resv.
Current problem is we don't pass resv anywhere except ALLOW_EVICT case.
If you have concern for overwritten, we have to do ".resv = bo->resv" in
every ttm_operation_ctx definitions.
-David
>
> 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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