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

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 07.05.19 um 13:22 schrieb zhoucm1:
>
>
> 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@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.

No, what I mean is to add the acquire_ctx as separate parameter to 
ttm_mem_evict_first().

E.g. we only need it in this function and it is actually not related to 
the ttm operation context filled in by the driver.

Christian.

>
> -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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