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

[zhoucm1 <zhoucm1@amd.com>]

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.

-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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