RE: [PATCH 01/11] drm/ttm: Make LRU removal optional.

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> -----Original Message-----
> From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
> Sent: Tuesday, May 14, 2019 8:31 PM
> To: Olsak, Marek <Marek.Olsak@xxxxxxx>; Zhou, David(ChunMing)
> <David1.Zhou@xxxxxxx>; Liang, Prike <Prike.Liang@xxxxxxx>; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Subject: [PATCH 01/11] drm/ttm: Make LRU removal optional.
> 
> [CAUTION: External Email]
> 
> We are already doing this for DMA-buf imports and also for amdgpu VM BOs
> for quite a while now.
> 
> If this doesn't run into any problems we are probably going to stop removing
> BOs from the LRU altogether.
> 
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
[snip]
> diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> index 0075eb9a0b52..957ec375a4ba 100644
> --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> @@ -69,7 +69,8 @@ void ttm_eu_backoff_reservation(struct
> ww_acquire_ctx *ticket,
>         list_for_each_entry(entry, list, head) {
>                 struct ttm_buffer_object *bo = entry->bo;
> 
> -               ttm_bo_add_to_lru(bo);
> +               if (list_empty(&bo->lru))
> +                       ttm_bo_add_to_lru(bo);
>                 reservation_object_unlock(bo->resv);
>         }
>         spin_unlock(&glob->lru_lock);
> @@ -93,7 +94,7 @@ EXPORT_SYMBOL(ttm_eu_backoff_reservation);
> 
>  int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
>                            struct list_head *list, bool intr,
> -                          struct list_head *dups)
> +                          struct list_head *dups, bool del_lru)
>  {
>         struct ttm_bo_global *glob;
>         struct ttm_validate_buffer *entry; @@ -172,11 +173,11 @@ int
> ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
>                 list_add(&entry->head, list);
>         }
> 
> -       if (ticket)
> -               ww_acquire_done(ticket);
> -       spin_lock(&glob->lru_lock);
> -       ttm_eu_del_from_lru_locked(list);
> -       spin_unlock(&glob->lru_lock);
> +       if (del_lru) {
> +               spin_lock(&glob->lru_lock);
> +               ttm_eu_del_from_lru_locked(list);
> +               spin_unlock(&glob->lru_lock);
> +       }

Can you make bo to lru tail here when del_lru is false?

Busy iteration in evict_first will try other process Bos first, which could save loop time.

>         return 0;
>  }
>  EXPORT_SYMBOL(ttm_eu_reserve_buffers);
> @@ -203,7 +204,10 @@ void ttm_eu_fence_buffer_objects(struct
> ww_acquire_ctx *ticket,
>                         reservation_object_add_shared_fence(bo->resv, fence);
>                 else
>                         reservation_object_add_excl_fence(bo->resv, fence);
> -               ttm_bo_add_to_lru(bo);
> +               if (list_empty(&bo->lru))
> +                       ttm_bo_add_to_lru(bo);
> +               else
> +                       ttm_bo_move_to_lru_tail(bo, NULL);

If this line is done in above, then we don't need this here.

-David
>                 reservation_object_unlock(bo->resv);
>         }
>         spin_unlock(&glob->lru_lock);
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index 161b80fee492..5cffaa24259f 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -63,7 +63,7 @@ static int virtio_gpu_object_list_validate(struct
> ww_acquire_ctx *ticket,
>         struct virtio_gpu_object *qobj;
>         int ret;
> 
> -       ret = ttm_eu_reserve_buffers(ticket, head, true, NULL);
> +       ret = ttm_eu_reserve_buffers(ticket, head, true, NULL, true);
>         if (ret != 0)
>                 return ret;
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> index a7c30e567f09..d28cbedba0b5 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> @@ -465,7 +465,8 @@ vmw_resource_check_buffer(struct ww_acquire_ctx
> *ticket,
>         val_buf->bo = &res->backup->base;
>         val_buf->num_shared = 0;
>         list_add_tail(&val_buf->head, &val_list);
> -       ret = ttm_eu_reserve_buffers(ticket, &val_list, interruptible, NULL);
> +       ret = ttm_eu_reserve_buffers(ticket, &val_list, interruptible, NULL,
> +                                    true);
>         if (unlikely(ret != 0))
>                 goto out_no_reserve;
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_validation.h
> b/drivers/gpu/drm/vmwgfx/vmwgfx_validation.h
> index 3b396fea40d7..ac435b51f4eb 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_validation.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_validation.h
> @@ -165,7 +165,7 @@ vmw_validation_bo_reserve(struct
> vmw_validation_context *ctx,
>                           bool intr)
>  {
>         return ttm_eu_reserve_buffers(&ctx->ticket, &ctx->bo_list, intr,
> -                                     NULL);
> +                                     NULL, true);
>  }
> 
>  /**
> diff --git a/include/drm/ttm/ttm_bo_driver.h
> b/include/drm/ttm/ttm_bo_driver.h index c008346c2401..fc0d995ac90d
> 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -769,7 +769,10 @@ static inline void ttm_bo_unreserve(struct
> ttm_buffer_object *bo)  {
>         if (!(bo->mem.placement & TTM_PL_FLAG_NO_EVICT)) {
>                 spin_lock(&bo->bdev->glob->lru_lock);
> -               ttm_bo_add_to_lru(bo);
> +               if (list_empty(&bo->lru))
> +                       ttm_bo_add_to_lru(bo);
> +               else
> +                       ttm_bo_move_to_lru_tail(bo, NULL);
>                 spin_unlock(&bo->bdev->glob->lru_lock);
>         }
>         reservation_object_unlock(bo->resv);
> diff --git a/include/drm/ttm/ttm_execbuf_util.h
> b/include/drm/ttm/ttm_execbuf_util.h
> index 621615fa7728..7e46cc678e7e 100644
> --- a/include/drm/ttm/ttm_execbuf_util.h
> +++ b/include/drm/ttm/ttm_execbuf_util.h
> @@ -70,6 +70,7 @@ extern void ttm_eu_backoff_reservation(struct
> ww_acquire_ctx *ticket,
>   * @list:    thread private list of ttm_validate_buffer structs.
>   * @intr:    should the wait be interruptible
>   * @dups:    [out] optional list of duplicates.
> + * @del_lru: true if BOs should be removed from the LRU.
>   *
>   * Tries to reserve bos pointed to by the list entries for validation.
>   * If the function returns 0, all buffers are marked as "unfenced", @@ -98,7
> +99,7 @@ extern void ttm_eu_backoff_reservation(struct ww_acquire_ctx
> *ticket,
> 
>  extern int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
>                                   struct list_head *list, bool intr,
> -                                 struct list_head *dups);
> +                                 struct list_head *dups, bool del_lru);
> 
>  /**
>   * function ttm_eu_fence_buffer_objects.
> --
> 2.17.1

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