On Tue, Jun 18, 2024 at 09:18:12AM +0200, Thomas Hellström wrote:
Ugh, replying to correct version again...
> To address the problem with hitches moving when bulk move
> sublists are lru-bumped, register the list cursors with the
> ttm_lru_bulk_move structure when traversing its list, and
> when lru-bumping the list, move the cursor hitch to the tail.
- So the hitch moves to the tail (last) which points to the next item in
the LRU list
- Then bulk is moved which is from first -> last to the end of the LRU
list
- Now the hitch remains in the correct position in the list (i.e. it
didn't move with the bulk)
Did I get that right?
> This also means it's mandatory for drivers to call
> ttm_lru_bulk_move_init() and ttm_lru_bulk_move_fini() when
> initializing and finalizing the bulk move structure, so add
> those calls to the amdgpu- and xe driver.
>
> Compared to v1 this is slightly more code but less fragile
> and hopefully easier to understand.
>
> Changes in previous series:
> - Completely rework the functionality
> - Avoid a NULL pointer dereference assigning manager->mem_type
> - Remove some leftover code causing build problems
> v2:
> - For hitch bulk tail moves, store the mem_type in the cursor
> instead of with the manager.
> v3:
> - Remove leftover mem_type member from change in v2.
>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@xxxxxxx>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 ++
> drivers/gpu/drm/ttm/ttm_resource.c | 89 ++++++++++++++++++++++++++
> drivers/gpu/drm/xe/xe_vm.c | 4 ++
> include/drm/ttm/ttm_resource.h | 56 ++++++++++------
> 4 files changed, 132 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 3abfa66d72a2..97743993d711 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -2420,6 +2420,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
> if (r)
> return r;
>
> + ttm_lru_bulk_move_init(&vm->lru_bulk_move);
> +
> vm->is_compute_context = false;
>
> vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode &
> @@ -2484,6 +2486,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
> error_free_delayed:
> dma_fence_put(vm->last_tlb_flush);
> dma_fence_put(vm->last_unlocked);
> + ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
> amdgpu_vm_fini_entities(vm);
>
> return r;
> @@ -2640,6 +2643,7 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
> }
> }
>
> + ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
> }
>
> /**
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index 9c8b6499edfb..a03090683e79 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -33,6 +33,49 @@
>
> #include <drm/drm_util.h>
>
> +/* Detach the cursor from the bulk move list*/
> +static void
> +ttm_resource_cursor_clear_bulk(struct ttm_resource_cursor *cursor)
> +{
A lockdep annotation wouldn't hurt here.
> + cursor->bulk = NULL;
> + list_del_init(&cursor->bulk_link);
> +}
> +
> +/* Move the cursor to the end of the bulk move list it's in */
> +static void ttm_resource_cursor_move_bulk_tail(struct ttm_lru_bulk_move *bulk,
> + struct ttm_resource_cursor *cursor)
> +{
> + struct ttm_lru_bulk_move_pos *pos;
> +
A lockdep annotation wouldn't hurt here too.
> + if (WARN_ON_ONCE(bulk != cursor->bulk)) {
> + list_del_init(&cursor->bulk_link);
> + return;
> + }
> +
> + pos = &bulk->pos[cursor->mem_type][cursor->priority];
> + if (pos)
'if (pos->last)'?
As 'if (pos)' is going to always be true given you are using the address
of operator (&) on an instantiated struct ttm_lru_bulk_move_pos.
> + list_move(&cursor->hitch.link, &pos->last->lru.link);
This should be list_move_tail, right? So last->next == hitch.
As the code is last->prev == hitch which means the hitch would be
included in the bulk move, right?
> + ttm_resource_cursor_clear_bulk(cursor);
> +}
> +
> +/* Move all cursors attached to a bulk move to its end */
> +static void ttm_bulk_move_adjust_cursors(struct ttm_lru_bulk_move *bulk)
> +{
> + struct ttm_resource_cursor *cursor, *next;
> +
> + list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
> + ttm_resource_cursor_move_bulk_tail(bulk, cursor);
> +}
> +
> +/* Remove a cursor from an empty bulk move list */
> +static void ttm_bulk_move_drop_cursors(struct ttm_lru_bulk_move *bulk)
> +{
> + struct ttm_resource_cursor *cursor, *next;
> +
> + list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
> + ttm_resource_cursor_clear_bulk(cursor);
> +}
> +
> /**
> * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
> * @cursor: The struct ttm_resource_cursor to finalize.
> @@ -45,6 +88,7 @@ void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
> {
> lockdep_assert_held(&cursor->man->bdev->lru_lock);
> list_del_init(&cursor->hitch.link);
> + ttm_resource_cursor_clear_bulk(cursor);
> }
>
> /**
> @@ -73,9 +117,27 @@ void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
> void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk)
> {
> memset(bulk, 0, sizeof(*bulk));
> + INIT_LIST_HEAD(&bulk->cursor_list);
> }
> EXPORT_SYMBOL(ttm_lru_bulk_move_init);
>
> +/**
> + * ttm_lru_bulk_move_fini - finalize a bulk move structure
> + * @bdev: The struct ttm_device
> + * @bulk: the structure to finalize
> + *
> + * Sanity checks that bulk moves don't have any
> + * resources left and hence no cursors attached.
> + */
> +void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
> + struct ttm_lru_bulk_move *bulk)
> +{
> + spin_lock(&bdev->lru_lock);
> + ttm_bulk_move_drop_cursors(bulk);
> + spin_unlock(&bdev->lru_lock);
> +}
> +EXPORT_SYMBOL(ttm_lru_bulk_move_fini);
> +
> /**
> * ttm_lru_bulk_move_tail - bulk move range of resources to the LRU tail.
> *
> @@ -88,6 +150,7 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
> {
> unsigned i, j;
>
> + ttm_bulk_move_adjust_cursors(bulk);
> for (i = 0; i < TTM_NUM_MEM_TYPES; ++i) {
> for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
> struct ttm_lru_bulk_move_pos *pos = &bulk->pos[i][j];
> @@ -515,6 +578,29 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
> }
> EXPORT_SYMBOL(ttm_resource_manager_debug);
>
> +static void
> +ttm_resource_cursor_check_bulk(struct ttm_resource_cursor *cursor,
> + struct ttm_lru_item *next_lru)
> +{
> + struct ttm_resource *next = ttm_lru_item_to_res(next_lru);
> + struct ttm_lru_bulk_move *bulk = NULL;
> + struct ttm_buffer_object *bo = next->bo;
> +
> + lockdep_assert_held(&cursor->man->bdev->lru_lock);
> + if (bo && bo->resource == next)
> + bulk = bo->bulk_move;
Can you explain what the above if statement is doing, struggling a bit
here. Is this a weird case where the LRU item (struct ttm_resource) is
fully (1st condition) or partially (2nd condition) detached from a BO?
> +
> + if (cursor->bulk != bulk) {
> + if (bulk) {
> + list_move_tail(&cursor->bulk_link, &bulk->cursor_list);
> + cursor->mem_type = next->mem_type;
> + } else {
> + list_del_init(&cursor->bulk_link);
> + }
> + cursor->bulk = bulk;
> + }
> +}
> +
> /**
> * ttm_resource_manager_first() - Start iterating over the resources
> * of a resource manager
> @@ -535,6 +621,7 @@ ttm_resource_manager_first(struct ttm_resource_manager *man,
> cursor->priority = 0;
> cursor->man = man;
> ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
> + INIT_LIST_HEAD(&cursor->bulk_link);
> list_add(&cursor->hitch.link, &man->lru[cursor->priority]);
>
> return ttm_resource_manager_next(cursor);
> @@ -559,6 +646,7 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
> lru = &cursor->hitch;
> list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> if (ttm_lru_item_is_res(lru)) {
> + ttm_resource_cursor_check_bulk(cursor, lru);
> list_move(&cursor->hitch.link, &lru->link);
Sorry noticing this here from a different patch. Shouldn't this be
list_move_tail so if the LRU can't be evicted we don't pick it again?
Matt
> return ttm_lru_item_to_res(lru);
> }
> @@ -568,6 +656,7 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
> break;
>
> list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
> + ttm_resource_cursor_clear_bulk(cursor);
> }
>
> ttm_resource_cursor_fini_locked(cursor);
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 61d4d95a5377..226da3c74f9c 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -1339,6 +1339,8 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
>
> INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
>
> + ttm_lru_bulk_move_init(&vm->lru_bulk_move);
> +
> INIT_LIST_HEAD(&vm->preempt.exec_queues);
> vm->preempt.min_run_period_ms = 10; /* FIXME: Wire up to uAPI */
>
> @@ -1462,6 +1464,7 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
> mutex_destroy(&vm->snap_mutex);
> for_each_tile(tile, xe, id)
> xe_range_fence_tree_fini(&vm->rftree[id]);
> + ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
> kfree(vm);
> if (flags & XE_VM_FLAG_LR_MODE)
> xe_pm_runtime_put(xe);
> @@ -1605,6 +1608,7 @@ static void vm_destroy_work_func(struct work_struct *w)
> XE_WARN_ON(vm->pt_root[id]);
>
> trace_xe_vm_free(vm);
> + ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
> kfree(vm);
> }
>
> diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
> index 8fac781f641e..571abb4861a6 100644
> --- a/include/drm/ttm/ttm_resource.h
> +++ b/include/drm/ttm/ttm_resource.h
> @@ -269,26 +269,6 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
> return container_of(item, struct ttm_resource, lru);
> }
>
> -/**
> - * struct ttm_resource_cursor
> - *
> - * @man: The resource manager currently being iterated over.
> - * @hitch: A hitch list node inserted before the next resource
> - * to iterate over.
> - * @priority: the current priority
> - *
> - * Cursor to iterate over the resources in a manager.
> - */
> -struct ttm_resource_cursor {
> - struct ttm_resource_manager *man;
> - struct ttm_lru_item hitch;
> - unsigned int priority;
> -};
> -
> -void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
> -
> -void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
> -
> /**
> * struct ttm_lru_bulk_move_pos
> *
> @@ -304,8 +284,9 @@ struct ttm_lru_bulk_move_pos {
>
> /**
> * struct ttm_lru_bulk_move
> - *
> * @pos: first/last lru entry for resources in the each domain/priority
> + * @cursor_list: The list of cursors currently traversing any of
> + * the sublists of @pos. Protected by the ttm device's lru_lock.
> *
> * Container for the current bulk move state. Should be used with
> * ttm_lru_bulk_move_init() and ttm_bo_set_bulk_move().
> @@ -315,8 +296,39 @@ struct ttm_lru_bulk_move_pos {
> */
> struct ttm_lru_bulk_move {
> struct ttm_lru_bulk_move_pos pos[TTM_NUM_MEM_TYPES][TTM_MAX_BO_PRIORITY];
> + struct list_head cursor_list;
> };
>
> +/**
> + * struct ttm_resource_cursor
> + * @man: The resource manager currently being iterated over
> + * @hitch: A hitch list node inserted before the next resource
> + * to iterate over.
> + * @bulk_link: A list link for the list of cursors traversing the
> + * bulk sublist of @bulk. Protected by the ttm device's lru_lock.
> + * @bulk: Pointer to struct ttm_lru_bulk_move whose subrange @hitch is
> + * inserted to. NULL if none. Never dereference this pointer since
> + * the struct ttm_lru_bulk_move object pointed to might have been
> + * freed. The pointer is only for comparison.
> + * @mem_type: The memory type of the LRU list being traversed.
> + * This field is valid iff @bulk != NULL.
> + * @priority: the current priority
> + *
> + * Cursor to iterate over the resources in a manager.
> + */
> +struct ttm_resource_cursor {
> + struct ttm_resource_manager *man;
> + struct ttm_lru_item hitch;
> + struct list_head bulk_link;
> + struct ttm_lru_bulk_move *bulk;
> + unsigned int mem_type;
> + unsigned int priority;
> +};
> +
> +void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
> +
> +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
> +
> /**
> * struct ttm_kmap_iter_iomap - Specialization for a struct io_mapping +
> * struct sg_table backed struct ttm_resource.
> @@ -405,6 +417,8 @@ ttm_resource_manager_cleanup(struct ttm_resource_manager *man)
>
> void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk);
> void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk);
> +void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
> + struct ttm_lru_bulk_move *bulk);
>
> void ttm_resource_add_bulk_move(struct ttm_resource *res,
> struct ttm_buffer_object *bo);
> --
> 2.44.0
>
