Re: [PATCH 7/7] drm/ttm: optimize ttm_mem_evict_first v2

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 10.11.2017 um 08:22 schrieb Chunming Zhou:
> On 2017年11月09日 16:59, Christian König wrote:
> > Deleted BOs with the same reservation object can be reaped even if they
> > can't be reserved.
> >
> > v2: rebase and we still need to remove/add the BO from/to the LRU.
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo.c | 39 
> > +++++++++++++++++++++++++++++++--------
> >   1 file changed, 31 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > index 50a678b504f3..6545c4344684 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -735,20 +735,37 @@ bool ttm_bo_eviction_valuable(struct 
> > ttm_buffer_object *bo,
> >   EXPORT_SYMBOL(ttm_bo_eviction_valuable);
> >     static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> > -                uint32_t mem_type,
> > -                const struct ttm_place *place,
> > -                bool interruptible,
> > -                bool no_wait_gpu)
> > +                   struct reservation_object *resv,
> > +                   uint32_t mem_type,
> > +                   const struct ttm_place *place,
> > +                   bool interruptible,
> > +                   bool no_wait_gpu)
> >   {
> >       struct ttm_bo_global *glob = bdev->glob;
> >       struct ttm_mem_type_manager *man = &bdev->man[mem_type];
> >       struct ttm_buffer_object *bo;
> >       int ret = -EBUSY;
> > +    bool locked;
> >       unsigned i;
> >         spin_lock(&glob->lru_lock);
> >       for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> >           list_for_each_entry(bo, &man->lru[i], lru) {
> > +            if (bo->resv == resv) {
> > +                if (list_empty(&bo->ddestroy))
> > +                    continue;
> I don't think only destroying BO can be evicted under per-vm-bo case, 
> but also normal BO should as well.
> I'd give an example:
> 1. vm-A allocates all vram;
> 2. vm-B also try to allocate full vram, so the BOs of vram in vm-A 
> will be evicted to GTT.
> 3. vm-A is trying to allocate all GTT, if we don't allow eviction or 
> swap, then will fail here.

That is a really good example, thanks.

> As above, we shouldn't disallow eviction and swap during allocation, 
> we aren't able to predict what case happen.
> For over limit allocation, at worst, they will be returned with failed 
> status while doing its CS.
> If you think the allocation shouldn't be over limitation of memory, we 
> can add the checking condition before allocation every time, but not 
> disallow eviction and swap in allocation, which really breaks the used 
> TTM.

Ok, you convinced me. The case above indeed needs a better handling.

I will reactivate my operation context patch set for TTM. Shouldn't be 
to much work to get this going.

Regards,
Christian.

> Regards,
> David Zhou
>
> > +
> > +                if (place &&
> > +                    !bdev->driver->eviction_valuable(bo, place))
> > +                    continue;
> > +
> > +                ttm_bo_del_from_lru(bo);
> > +
> > +                ret = 0;
> > +                locked = false;
> > +                break;
> > +            }
> > +
> >               ret = reservation_object_trylock(bo->resv) ? 0 : -EBUSY;
> >               if (ret)
> >                   continue;
> > @@ -760,6 +777,7 @@ static int ttm_mem_evict_first(struct 
> > ttm_bo_device *bdev,
> >                   continue;
> >               }
> >   +            locked = true;
> >               break;
> >           }
> >   @@ -775,7 +793,8 @@ static int ttm_mem_evict_first(struct 
> > ttm_bo_device *bdev,
> >       kref_get(&bo->list_kref);
> >         if (!list_empty(&bo->ddestroy)) {
> > -        ret = ttm_bo_cleanup_refs(bo, interruptible, no_wait_gpu, 
> > true);
> > +        ret = ttm_bo_cleanup_refs(bo, interruptible, no_wait_gpu,
> > +                      locked);
> >           kref_put(&bo->list_kref, ttm_bo_release_list);
> >           return ret;
> >       }
> > @@ -786,7 +805,10 @@ static int ttm_mem_evict_first(struct 
> > ttm_bo_device *bdev,
> >       BUG_ON(ret != 0);
> >         ret = ttm_bo_evict(bo, interruptible, no_wait_gpu);
> > -    ttm_bo_unreserve(bo);
> > +    if (locked)
> > +        ttm_bo_unreserve(bo);
> > +    else
> > +        ttm_bo_add_to_lru(bo);
> >         kref_put(&bo->list_kref, ttm_bo_release_list);
> >       return ret;
> > @@ -850,7 +872,7 @@ 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,
> > +        ret = ttm_mem_evict_first(bdev, bo->resv, mem_type, place,
> >                         interruptible, no_wait_gpu);
> >           if (unlikely(ret != 0))
> >               return ret;
> > @@ -1353,7 +1375,8 @@ static int ttm_bo_force_list_clean(struct 
> > ttm_bo_device *bdev,
> >       for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> >           while (!list_empty(&man->lru[i])) {
> >               spin_unlock(&glob->lru_lock);
> > -            ret = ttm_mem_evict_first(bdev, mem_type, NULL, false, 
> > false);
> > +            ret = ttm_mem_evict_first(bdev, NULL, mem_type, NULL,
> > +                          false, false);
> >               if (ret)
> >                   return ret;
> >               spin_lock(&glob->lru_lock);

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