[PATCH 1/2] [WIP]drm/ttm: add waiter list to prevent allocation not in order

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Am 05.02.2018 um 09:22 schrieb Chunming Zhou:
> On 2018å¹´01æ??31æ?¥ 18:54, Christian König wrote:
>>> So I think preventing validation on same place is a simpler way:
>>> process B bo's place is fpfn~lpfn, it will only try to evict LRU BOs 
>>> in that range, while eviction, we just prevent those validation to 
>>> this range(fpfn~lpfn), if out of this range, the 
>>> allocation/validation still can be go on.
>>>
>>> Any negative?
>> That won't work either. The most common use of fpfn~lpfn range is to 
>> limit a BO to visible VRAM, the other use cases are to fullfil 
>> hardware limitations.
>>
>> So blocking this would result in blocking all normal GTT and VRAM 
>> allocations, adding a mutex to validate would have the same effect.
> No, different effect, mutex will make the every allocation serialized. 
> My approach only effects busy case, that is said, only when space is 
> used up, the allocation is serialized in that range, otherwise still 
> in parallel.

That would still not allow for concurrent evictions, not as worse as 
completely blocking concurrent validation but still not a good idea as 
far as I can see.

Going to give it a try today to use the ww_mutex owner to detect 
eviction of already reserved BOs.

Maybe that can be used instead,
Christian.

>
> Regards,
> David Zhou
>
>
>>
>> Regards,
>> Christian.
>>
>> Am 31.01.2018 um 11:30 schrieb Chunming Zhou:
>>>
>>>
>>>
>>> On 2018å¹´01æ??26æ?¥ 22:35, Christian König wrote:
>>>> I just realized that a change I'm thinking about for a while would 
>>>> solve your problem as well, but keep concurrent allocation possible.
>>>>
>>>> See ttm_mem_evict_first() unlocks the BO after evicting it:
>>>>>         ttm_bo_del_from_lru(bo);
>>>>>         spin_unlock(&glob->lru_lock);
>>>>>
>>>>>         ret = ttm_bo_evict(bo, ctx);
>>>>>         if (locked) {
>>>>>                 ttm_bo_unreserve(bo); <-------- here
>>>>>         } else {
>>>>>                 spin_lock(&glob->lru_lock);
>>>>>                 ttm_bo_add_to_lru(bo);
>>>>>                 spin_unlock(&glob->lru_lock);
>>>>>         }
>>>>>
>>>>>         kref_put(&bo->list_kref, ttm_bo_release_list);
>>>>
>>>> The effect is that in your example process C can not only beat 
>>>> process B once, but many many times because we run into a ping/pong 
>>>> situation where B evicts resources while C moves them back in.
>>> For ping/pong case, I want to disable busy placement for allocation 
>>> period, only enable it for cs bo validation.
>>>
>>>>
>>>> For a while now I'm thinking about dropping those reservations only 
>>>> after the original allocation succeeded.
>>>>
>>>> The effect would be that process C can still beat process B 
>>>> initially, but sooner or process B would evict some resources from 
>>>> process C as well and then it can succeed with its allocation.
>>> If it is from process C cs validation, process B still need evict 
>>> the resource only after process C command submission completion.
>>>
>>>>
>>>> The problem is for this approach to work we need to core change to 
>>>> the ww_mutexes to be able to handle this efficiently.
>>> Yes, ww_mutex doesn't support this net lock, which easily deadlock 
>>> without ticket and class.
>>>
>>> So I think preventing validation on same place is a simpler way:
>>> process B bo's place is fpfn~lpfn, it will only try to evict LRU BOs 
>>> in that range, while eviction, we just prevent those validation to 
>>> this range(fpfn~lpfn), if out of this range, the 
>>> allocation/validation still can be go on.
>>>
>>> Any negative?
>>>
>>> Regards,
>>> David Zhou
>>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>> Am 26.01.2018 um 14:59 schrieb Christian König:
>>>>> I know, but this has the same effect. You prevent concurrent 
>>>>> allocation from happening.
>>>>>
>>>>> What we could do is to pipeline reusing of deleted memory as well, 
>>>>> this makes it less likely to cause the problem you are seeing 
>>>>> because the evicting processes doesn't need to block for deleted 
>>>>> BOs any more.
>>>>>
>>>>> But that other processes can grab memory during eviction is 
>>>>> intentional. Otherwise greedy processes would completely dominate 
>>>>> command submission.
>>>>>
>>>>> Regards,
>>>>> Christian.
>>>>>
>>>>> Am 26.01.2018 um 14:50 schrieb Zhou, David(ChunMing):
>>>>>> I don't want to prevent all, my new approach is to prevent the 
>>>>>> later allocation is trying and ahead of front to get the memory 
>>>>>> space that the front made from eviction.
>>>>>>
>>>>>>
>>>>>> å??è?ªå??æ?? Pro
>>>>>>
>>>>>> Christian Ké°?ig <ckoenig.leichtzumerken at gmail.com> äº? 2018å¹´1æ??26æ?¥ 
>>>>>> ä¸?å??9:24å??é??ï¼?
>>>>>>
>>>>>> Yes, exactly that's the problem.
>>>>>>
>>>>>> See when you want to prevent a process B from allocating the 
>>>>>> memory process A has evicted, you need to prevent all concurrent 
>>>>>> allocation.
>>>>>>
>>>>>> And we don't do that because it causes a major performance drop.
>>>>>>
>>>>>> Regards,
>>>>>> Christian.
>>>>>>
>>>>>> Am 26.01.2018 um 14:21 schrieb Zhou, David(ChunMing):
>>>>>>> You patch will prevent concurrent allocation, and will result in 
>>>>>>> allocation performance drop much.
>>>>>>>
>>>>>>> å??è?ªå??æ?? Pro
>>>>>>>
>>>>>>> Christian Ké°?ig <ckoenig.leichtzumerken at gmail.com> äº? 2018å¹´1æ??26æ?¥ 
>>>>>>> ä¸?å??9:04å??é??ï¼?
>>>>>>>
>>>>>>> Attached is what you actually want to do cleanly implemented. 
>>>>>>> But as I said this is a NO-GO.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Christian.
>>>>>>>
>>>>>>> Am 26.01.2018 um 13:43 schrieb Christian König:
>>>>>>>>> After my investigation, this issue should be detect of TTM 
>>>>>>>>> design self, which breaks scheduling balance.
>>>>>>>> Yeah, but again. This is indented design we can't change easily.
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>> Christian.
>>>>>>>>
>>>>>>>> Am 26.01.2018 um 13:36 schrieb Zhou, David(ChunMing):
>>>>>>>>> I am off work, so reply mail by phone, the format could not be 
>>>>>>>>> text.
>>>>>>>>>
>>>>>>>>> back to topic itself:
>>>>>>>>> the problem indeed happen on amdgpu driver, someone reports me 
>>>>>>>>> that application runs with two instances, the performance are 
>>>>>>>>> different.
>>>>>>>>> I also reproduced the issue with unit test(bo_eviction_test). 
>>>>>>>>> They always think our scheduler isn't working as expected.
>>>>>>>>>
>>>>>>>>> After my investigation, this issue should be detect of TTM 
>>>>>>>>> design self, which breaks scheduling balance.
>>>>>>>>>
>>>>>>>>> Further, if we run containers for our gpu, container A could 
>>>>>>>>> run high score, container B runs low score with same benchmark.
>>>>>>>>>
>>>>>>>>> So this is bug that we need fix.
>>>>>>>>>
>>>>>>>>> Regards,
>>>>>>>>> David Zhou
>>>>>>>>>
>>>>>>>>> å??è?ªå??æ?? Pro
>>>>>>>>>
>>>>>>>>> Christian K�ig <ckoenig.leichtzumerken at gmail.com> � 
>>>>>>>>> 2018å¹´1æ??26æ?¥ ä¸?å??6:31å??é??ï¼?
>>>>>>>>>
>>>>>>>>> Am 26.01.2018 um 11:22 schrieb Chunming Zhou:
>>>>>>>>> > there is a scheduling balance issue about get node like:
>>>>>>>>> > a. process A allocates full memory and use it for submission.
>>>>>>>>> > b. process B tries to allocates memory, will wait for 
>>>>>>>>> process A BO idle in eviction.
>>>>>>>>> > c. process A completes the job, process B eviction will put 
>>>>>>>>> process A BO node,
>>>>>>>>> > but in the meantime, process C is comming to allocate BO, 
>>>>>>>>> whill directly get node successfully, and do submission,
>>>>>>>>> > process B will again wait for process C BO idle.
>>>>>>>>> > d. repeat the above setps, process B could be delayed much more.
>>>>>>>>> >
>>>>>>>>> > later allocation must not be ahead of front in same place.
>>>>>>>>>
>>>>>>>>> Again NAK to the whole approach.
>>>>>>>>>
>>>>>>>>> At least with amdgpu the problem you described above never occurs
>>>>>>>>> because evictions are pipelined operations. We could only 
>>>>>>>>> block for
>>>>>>>>> deleted regions to become free.
>>>>>>>>>
>>>>>>>>> But independent of that incoming memory requests while we make 
>>>>>>>>> room for
>>>>>>>>> eviction are intended to be served first.
>>>>>>>>>
>>>>>>>>> Changing that is certainly a no-go cause that would favor 
>>>>>>>>> memory hungry
>>>>>>>>> applications over small clients.
>>>>>>>>>
>>>>>>>>> Regards,
>>>>>>>>> Christian.
>>>>>>>>>
>>>>>>>>> >
>>>>>>>>> > Change-Id: I3daa892e50f82226c552cc008a29e55894a98f18
>>>>>>>>> > Signed-off-by: Chunming Zhou <david1.zhou at amd.com>
>>>>>>>>> > ---
>>>>>>>>> >   drivers/gpu/drm/ttm/ttm_bo.c    | 69 
>>>>>>>>> +++++++++++++++++++++++++++++++++++++++--
>>>>>>>>> >   include/drm/ttm/ttm_bo_api.h |  7 +++++
>>>>>>>>> >   include/drm/ttm/ttm_bo_driver.h |  7 +++++
>>>>>>>>> >   3 files changed, 80 insertions(+), 3 deletions(-)
>>>>>>>>> >
>>>>>>>>> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
>>>>>>>>> b/drivers/gpu/drm/ttm/ttm_bo.c
>>>>>>>>> > index d33a6bb742a1..558ec2cf465d 100644
>>>>>>>>> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
>>>>>>>>> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>>>>>>>>> > @@ -841,6 +841,58 @@ static int ttm_bo_add_move_fence(struct 
>>>>>>>>> ttm_buffer_object *bo,
>>>>>>>>> >        return 0;
>>>>>>>>> >   }
>>>>>>>>> >
>>>>>>>>> > +static void ttm_man_init_waiter(struct ttm_bo_waiter *waiter,
>>>>>>>>> > + struct ttm_buffer_object *bo,
>>>>>>>>> > +                             const struct ttm_place *place)
>>>>>>>>> > +{
>>>>>>>>> > +     waiter->tbo = bo;
>>>>>>>>> > +     memcpy((void *)&waiter->place, (void *)place, 
>>>>>>>>> sizeof(*place));
>>>>>>>>> > + INIT_LIST_HEAD(&waiter->list);
>>>>>>>>> > +}
>>>>>>>>> > +
>>>>>>>>> > +static void ttm_man_add_waiter(struct ttm_mem_type_manager 
>>>>>>>>> *man,
>>>>>>>>> > +                            struct ttm_bo_waiter *waiter)
>>>>>>>>> > +{
>>>>>>>>> > +     if (!waiter)
>>>>>>>>> > +             return;
>>>>>>>>> > + spin_lock(&man->wait_lock);
>>>>>>>>> > + list_add_tail(&waiter->list, &man->waiter_list);
>>>>>>>>> > + spin_unlock(&man->wait_lock);
>>>>>>>>> > +}
>>>>>>>>> > +
>>>>>>>>> > +static void ttm_man_del_waiter(struct ttm_mem_type_manager 
>>>>>>>>> *man,
>>>>>>>>> > +                            struct ttm_bo_waiter *waiter)
>>>>>>>>> > +{
>>>>>>>>> > +     if (!waiter)
>>>>>>>>> > +             return;
>>>>>>>>> > + spin_lock(&man->wait_lock);
>>>>>>>>> > +     if (!list_empty(&waiter->list))
>>>>>>>>> > + list_del(&waiter->list);
>>>>>>>>> > + spin_unlock(&man->wait_lock);
>>>>>>>>> > +     kfree(waiter);
>>>>>>>>> > +}
>>>>>>>>> > +
>>>>>>>>> > +int ttm_man_check_bo(struct ttm_mem_type_manager *man,
>>>>>>>>> > +                  struct ttm_buffer_object *bo,
>>>>>>>>> > +                  const struct ttm_place *place)
>>>>>>>>> > +{
>>>>>>>>> > +     struct ttm_bo_waiter *waiter, *tmp;
>>>>>>>>> > +
>>>>>>>>> > + spin_lock(&man->wait_lock);
>>>>>>>>> > + list_for_each_entry_safe(waiter, tmp, &man->waiter_list, 
>>>>>>>>> list) {
>>>>>>>>> > +             if ((bo != waiter->tbo) &&
>>>>>>>>> > +                 ((place->fpfn >= waiter->place.fpfn &&
>>>>>>>>> > +                   place->fpfn <= waiter->place.lpfn) ||
>>>>>>>>> > +                  (place->lpfn <= waiter->place.lpfn && 
>>>>>>>>> place->lpfn >=
>>>>>>>>> > + waiter->place.fpfn)))
>>>>>>>>> > +                 goto later_bo;
>>>>>>>>> > +     }
>>>>>>>>> > + spin_unlock(&man->wait_lock);
>>>>>>>>> > +     return true;
>>>>>>>>> > +later_bo:
>>>>>>>>> > + spin_unlock(&man->wait_lock);
>>>>>>>>> > +     return false;
>>>>>>>>> > +}
>>>>>>>>> >   /**
>>>>>>>>> >    * Repeatedly evict memory from the LRU for @mem_type 
>>>>>>>>> until we create enough
>>>>>>>>> >    * space, or we've evicted everything and there isn't 
>>>>>>>>> enough space.
>>>>>>>>> > @@ -853,17 +905,26 @@ 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_bo_waiter waiter;
>>>>>>>>> >        int ret;
>>>>>>>>> >
>>>>>>>>> > + ttm_man_init_waiter(&waiter, bo, place);
>>>>>>>>> > +     ttm_man_add_waiter(man, &waiter);
>>>>>>>>> >        do {
>>>>>>>>> >                ret = (*man->func->get_node)(man, bo, place, 
>>>>>>>>> mem);
>>>>>>>>> > -             if (unlikely(ret != 0))
>>>>>>>>> > +             if (unlikely(ret != 0)) {
>>>>>>>>> > + ttm_man_del_waiter(man, &waiter);
>>>>>>>>> >                        return ret;
>>>>>>>>> > -             if (mem->mm_node)
>>>>>>>>> > +             }
>>>>>>>>> > +             if (mem->mm_node) {
>>>>>>>>> > + ttm_man_del_waiter(man, &waiter);
>>>>>>>>> >                        break;
>>>>>>>>> > +             }
>>>>>>>>> >                ret = ttm_mem_evict_first(bdev, mem_type, 
>>>>>>>>> place, ctx);
>>>>>>>>> > -             if (unlikely(ret != 0))
>>>>>>>>> > +             if (unlikely(ret != 0)) {
>>>>>>>>> > + ttm_man_del_waiter(man, &waiter);
>>>>>>>>> >                        return ret;
>>>>>>>>> > +             }
>>>>>>>>> >        } while (1);
>>>>>>>>> >        mem->mem_type = mem_type;
>>>>>>>>> >        return ttm_bo_add_move_fence(bo, man, mem);
>>>>>>>>> > @@ -1450,6 +1511,8 @@ int ttm_bo_init_mm(struct 
>>>>>>>>> ttm_bo_device *bdev, unsigned type,
>>>>>>>>> >        man->use_io_reserve_lru = false;
>>>>>>>>> > mutex_init(&man->io_reserve_mutex);
>>>>>>>>> > spin_lock_init(&man->move_lock);
>>>>>>>>> > + spin_lock_init(&man->wait_lock);
>>>>>>>>> > + INIT_LIST_HEAD(&man->waiter_list);
>>>>>>>>> > INIT_LIST_HEAD(&man->io_reserve_lru);
>>>>>>>>> >
>>>>>>>>> >        ret = bdev->driver->init_mem_type(bdev, type, man);
>>>>>>>>> > diff --git a/include/drm/ttm/ttm_bo_api.h 
>>>>>>>>> b/include/drm/ttm/ttm_bo_api.h
>>>>>>>>> > index 2cd025c2abe7..0fce4dbd02e7 100644
>>>>>>>>> > --- a/include/drm/ttm/ttm_bo_api.h
>>>>>>>>> > +++ b/include/drm/ttm/ttm_bo_api.h
>>>>>>>>> > @@ -40,6 +40,7 @@
>>>>>>>>> >   #include <linux/mm.h>
>>>>>>>>> >   #include <linux/bitmap.h>
>>>>>>>>> >   #include <linux/reservation.h>
>>>>>>>>> > +#include <drm/ttm/ttm_placement.h>
>>>>>>>>> >
>>>>>>>>> >   struct ttm_bo_device;
>>>>>>>>> >
>>>>>>>>> > @@ -232,6 +233,12 @@ struct ttm_buffer_object {
>>>>>>>>> >        struct mutex wu_mutex;
>>>>>>>>> >   };
>>>>>>>>> >
>>>>>>>>> > +struct ttm_bo_waiter {
>>>>>>>>> > +     struct ttm_buffer_object *tbo;
>>>>>>>>> > +     struct ttm_place place;
>>>>>>>>> > +     struct list_head list;
>>>>>>>>> > +};
>>>>>>>>> > +
>>>>>>>>> >   /**
>>>>>>>>> >    * struct ttm_bo_kmap_obj
>>>>>>>>> >    *
>>>>>>>>> > diff --git a/include/drm/ttm/ttm_bo_driver.h 
>>>>>>>>> b/include/drm/ttm/ttm_bo_driver.h
>>>>>>>>> > index 9b417eb2df20..dc6b8b4c9e06 100644
>>>>>>>>> > --- a/include/drm/ttm/ttm_bo_driver.h
>>>>>>>>> > +++ b/include/drm/ttm/ttm_bo_driver.h
>>>>>>>>> > @@ -293,6 +293,10 @@ struct ttm_mem_type_manager {
>>>>>>>>> >        bool io_reserve_fastpath;
>>>>>>>>> >        spinlock_t move_lock;
>>>>>>>>> >
>>>>>>>>> > +     /* waiters in list */
>>>>>>>>> > +     spinlock_t wait_lock;
>>>>>>>>> > +     struct list_head waiter_list;
>>>>>>>>> > +
>>>>>>>>> >        /*
>>>>>>>>> >         * Protected by @io_reserve_mutex:
>>>>>>>>> >         */
>>>>>>>>> > @@ -748,6 +752,9 @@ int ttm_bo_mem_space(struct 
>>>>>>>>> ttm_buffer_object *bo,
>>>>>>>>> >                     struct ttm_mem_reg *mem,
>>>>>>>>> >                     struct ttm_operation_ctx *ctx);
>>>>>>>>> >
>>>>>>>>> > +int ttm_man_check_bo(struct ttm_mem_type_manager *man,
>>>>>>>>> > +                  struct ttm_buffer_object *bo,
>>>>>>>>> > +                  const struct ttm_place *place);
>>>>>>>>> >   void ttm_bo_mem_put(struct ttm_buffer_object *bo, struct 
>>>>>>>>> ttm_mem_reg *mem);
>>>>>>>>> >   void ttm_bo_mem_put_locked(struct ttm_buffer_object *bo,
>>>>>>>>> >                           struct ttm_mem_reg *mem);
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> amd-gfx mailing list
>>>>>>>>> amd-gfx at lists.freedesktop.org
>>>>>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> dri-devel mailing list
>>>>>>> dri-devel at lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> amd-gfx mailing list
>>>>> amd-gfx at lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>
>>>
>>
>
>
>
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> amd-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

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