Hi, Matt, Christian,
On Wed, 2024-04-17 at 08:09 +0200, Christian König wrote:
> Am 17.04.24 um 03:15 schrieb Matthew Brost:
> > On Tue, Apr 16, 2024 at 12:07:22PM +0200, Thomas Hellström wrote:
> > > To be able to handle list unlocking while traversing the LRU
> > > list, we want the iterators not only to point to the next
> > > position of the list traversal, but to insert themselves as
> > > list nodes at that point to work around the fact that the
> > > next node might otherwise disappear from the list while
> > > the iterator is pointing to it.
> > >
> > > These list nodes need to be easily distinguishable from other
> > > list nodes so that others traversing the list can skip
> > > over them.
> > >
> > > So declare a struct ttm_lru_item, with a struct list_head member
> > > and a type enum. This will slightly increase the size of a
> > > struct ttm_resource.
> > >
> > > Changes in previous series:
> > > - Update enum ttm_lru_item_type documentation.
> > >
> > Patch itself makes sense to me. One style question (or maybe
> > suggestion?) below.
> >
> > > Cc: Christian König <christian.koenig@xxxxxxx>
> > > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@xxxxxxx>
> > > Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Thomas Hellström
> > > <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/ttm/ttm_device.c | 13 ++++--
> > > drivers/gpu/drm/ttm/ttm_resource.c | 70 ++++++++++++++++++++++-
> > > -------
> > > include/drm/ttm/ttm_resource.h | 51 +++++++++++++++++++++-
> > > 3 files changed, 110 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/ttm/ttm_device.c
> > > b/drivers/gpu/drm/ttm/ttm_device.c
> > > index 76027960054f..f27406e851e5 100644
> > > --- a/drivers/gpu/drm/ttm/ttm_device.c
> > > +++ b/drivers/gpu/drm/ttm/ttm_device.c
> > > @@ -270,17 +270,22 @@ EXPORT_SYMBOL(ttm_device_fini);
> > > static void ttm_device_clear_lru_dma_mappings(struct ttm_device
> > > *bdev,
> > > struct list_head
> > > *list)
> > > {
> > > - struct ttm_resource *res;
> > > + struct ttm_lru_item *lru;
> > >
> > > spin_lock(&bdev->lru_lock);
> > > - while ((res = list_first_entry_or_null(list,
> > > typeof(*res), lru))) {
> > > - struct ttm_buffer_object *bo = res->bo;
> > > + while ((lru = list_first_entry_or_null(list,
> > > typeof(*lru), link))) {
> > > + struct ttm_buffer_object *bo;
> > > +
> > > + if (!ttm_lru_item_is_res(lru))
> > > + continue;
> > > +
> > > + bo = ttm_lru_item_to_res(lru)->bo;
> > >
> > > /* Take ref against racing releases once
> > > lru_lock is unlocked */
> > > if (!ttm_bo_get_unless_zero(bo))
> > > continue;
> > >
> > > - list_del_init(&res->lru);
> > > + list_del_init(&bo->resource->lru.link);
> > > spin_unlock(&bdev->lru_lock);
> > >
> > > if (bo->ttm)
> > > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > > b/drivers/gpu/drm/ttm/ttm_resource.c
> > > index be8d286513f9..7aa5ca5c0e33 100644
> > > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > > @@ -69,8 +69,8 @@ void ttm_lru_bulk_move_tail(struct
> > > ttm_lru_bulk_move *bulk)
> > > dma_resv_assert_held(pos->last->bo-
> > > >base.resv);
> > >
> > > man = ttm_manager_type(pos->first->bo-
> > > >bdev, i);
> > > - list_bulk_move_tail(&man->lru[j], &pos-
> > > >first->lru,
> > > - &pos->last->lru);
> > > + list_bulk_move_tail(&man->lru[j], &pos-
> > > >first->lru.link,
> > > + &pos->last-
> > > >lru.link);
> > > }
> > > }
> > > }
> > > @@ -83,14 +83,38 @@ ttm_lru_bulk_move_pos(struct
> > > ttm_lru_bulk_move *bulk, struct ttm_resource *res)
> > > return &bulk->pos[res->mem_type][res->bo->priority];
> > > }
> > >
> > > +/* Return the previous resource on the list (skip over non-
> > > resource list items) */
> > > +static struct ttm_resource *ttm_lru_prev_res(struct ttm_resource
> > > *cur)
> > > +{
> > > + struct ttm_lru_item *lru = &cur->lru;
> > > +
> > > + do {
> > > + lru = list_prev_entry(lru, link);
> > > + } while (!ttm_lru_item_is_res(lru));
> > > +
> > > + return ttm_lru_item_to_res(lru);
> > > +}
> > > +
> > > +/* Return the next resource on the list (skip over non-resource
> > > list items) */
> > > +static struct ttm_resource *ttm_lru_next_res(struct ttm_resource
> > > *cur)
> > > +{
> > > + struct ttm_lru_item *lru = &cur->lru;
> > > +
> > > + do {
> > > + lru = list_next_entry(lru, link);
> > > + } while (!ttm_lru_item_is_res(lru));
> > > +
> > > + return ttm_lru_item_to_res(lru);
> > > +}
> > > +
> > > /* Move the resource to the tail of the bulk move range */
> > > static void ttm_lru_bulk_move_pos_tail(struct
> > > ttm_lru_bulk_move_pos *pos,
> > > struct ttm_resource *res)
> > > {
> > > if (pos->last != res) {
> > > if (pos->first == res)
> > > - pos->first = list_next_entry(res, lru);
> > > - list_move(&res->lru, &pos->last->lru);
> > > + pos->first = ttm_lru_next_res(res);
> > > + list_move(&res->lru.link, &pos->last->lru.link);
> > > pos->last = res;
> > > }
> > > }
> > > @@ -121,11 +145,11 @@ static void ttm_lru_bulk_move_del(struct
> > > ttm_lru_bulk_move *bulk,
> > > pos->first = NULL;
> > > pos->last = NULL;
> > > } else if (pos->first == res) {
> > > - pos->first = list_next_entry(res, lru);
> > > + pos->first = ttm_lru_next_res(res);
> > > } else if (pos->last == res) {
> > > - pos->last = list_prev_entry(res, lru);
> > > + pos->last = ttm_lru_prev_res(res);
> > > } else {
> > > - list_move(&res->lru, &pos->last->lru);
> > > + list_move(&res->lru.link, &pos->last->lru.link);
> > > }
> > > }
> > >
> > > @@ -154,7 +178,7 @@ void ttm_resource_move_to_lru_tail(struct
> > > ttm_resource *res)
> > > lockdep_assert_held(&bo->bdev->lru_lock);
> > >
> > > if (bo->pin_count) {
> > > - list_move_tail(&res->lru, &bdev->pinned);
> > > + list_move_tail(&res->lru.link, &bdev->pinned);
> > >
> > > } else if (bo->bulk_move) {
> > > struct ttm_lru_bulk_move_pos *pos =
> > > @@ -165,7 +189,7 @@ void ttm_resource_move_to_lru_tail(struct
> > > ttm_resource *res)
> > > struct ttm_resource_manager *man;
> > >
> > > man = ttm_manager_type(bdev, res->mem_type);
> > > - list_move_tail(&res->lru, &man->lru[bo-
> > > >priority]);
> > > + list_move_tail(&res->lru.link, &man->lru[bo-
> > > >priority]);
> > > }
> > > }
> > >
> > > @@ -196,9 +220,9 @@ void ttm_resource_init(struct
> > > ttm_buffer_object *bo,
> > > man = ttm_manager_type(bo->bdev, place->mem_type);
> > > spin_lock(&bo->bdev->lru_lock);
> > > if (bo->pin_count)
> > > - list_add_tail(&res->lru, &bo->bdev->pinned);
> > > + list_add_tail(&res->lru.link, &bo->bdev-
> > > >pinned);
> > > else
> > > - list_add_tail(&res->lru, &man->lru[bo-
> > > >priority]);
> > > + list_add_tail(&res->lru.link, &man->lru[bo-
> > > >priority]);
> > > man->usage += res->size;
> > > spin_unlock(&bo->bdev->lru_lock);
> > > }
> > > @@ -220,7 +244,7 @@ void ttm_resource_fini(struct
> > > ttm_resource_manager *man,
> > > struct ttm_device *bdev = man->bdev;
> > >
> > > spin_lock(&bdev->lru_lock);
> > > - list_del_init(&res->lru);
> > > + list_del_init(&res->lru.link);
> > > man->usage -= res->size;
> > > spin_unlock(&bdev->lru_lock);
> > > }
> > > @@ -471,14 +495,16 @@ struct ttm_resource *
> > > ttm_resource_manager_first(struct ttm_resource_manager *man,
> > > struct ttm_resource_cursor *cursor)
> > > {
> > > - struct ttm_resource *res;
> > > + struct ttm_lru_item *lru;
> > >
> > > lockdep_assert_held(&man->bdev->lru_lock);
> > >
> > > for (cursor->priority = 0; cursor->priority <
> > > TTM_MAX_BO_PRIORITY;
> > > ++cursor->priority)
> > > - list_for_each_entry(res, &man->lru[cursor-
> > > >priority], lru)
> > > - return res;
> > > + list_for_each_entry(lru, &man->lru[cursor-
> > > >priority], link) {
> > > + if (ttm_lru_item_is_res(lru))
> > > + return ttm_lru_item_to_res(lru);
> > > + }
> > >
> > > return NULL;
> > > }
> > > @@ -497,15 +523,21 @@ ttm_resource_manager_next(struct
> > > ttm_resource_manager *man,
> > > struct ttm_resource_cursor *cursor,
> > > struct ttm_resource *res)
> > > {
> > > + struct ttm_lru_item *lru = &res->lru;
> > > +
> > > lockdep_assert_held(&man->bdev->lru_lock);
> > >
> > > - list_for_each_entry_continue(res, &man->lru[cursor-
> > > >priority], lru)
> > > - return res;
> > > + list_for_each_entry_continue(lru, &man->lru[cursor-
> > > >priority], link) {
> > > + if (ttm_lru_item_is_res(lru))
> > > + return ttm_lru_item_to_res(lru);
> > > + }
> > >
> > > for (++cursor->priority; cursor->priority <
> > > TTM_MAX_BO_PRIORITY;
> > > ++cursor->priority)
> > > - list_for_each_entry(res, &man->lru[cursor-
> > > >priority], lru)
> > > - return res;
> > > + list_for_each_entry(lru, &man->lru[cursor-
> > > >priority], link) {
> > > + if (ttm_lru_item_is_res(lru))
> > > + ttm_lru_item_to_res(lru);
> > > + }
> > >
> > > return NULL;
> > > }
> > > diff --git a/include/drm/ttm/ttm_resource.h
> > > b/include/drm/ttm/ttm_resource.h
> > > index 69769355139f..4babc4ff10b0 100644
> > > --- a/include/drm/ttm/ttm_resource.h
> > > +++ b/include/drm/ttm/ttm_resource.h
> > > @@ -49,6 +49,43 @@ struct io_mapping;
> > > struct sg_table;
> > > struct scatterlist;
> > >
> > > +/**
> > > + * enum ttm_lru_item_type - enumerate ttm_lru_item subclasses
> > > + */
> > > +enum ttm_lru_item_type {
> > > + /** @TTM_LRU_RESOURCE: The resource subclass */
> > > + TTM_LRU_RESOURCE,
> > > + /** @TTM_LRU_HITCH: The iterator hitch subclass */
> > > + TTM_LRU_HITCH
> > > +};
> > > +
> > > +/**
> > > + * struct ttm_lru_item - The TTM lru list node base class
> > > + * @link: The list link
> > > + * @type: The subclass type
> > > + */
> > > +struct ttm_lru_item {
> > > + struct list_head link;
> > > + enum ttm_lru_item_type type;
> > > +};
> > > +
> > > +/**
> > > + * ttm_lru_item_init() - initialize a struct ttm_lru_item
> > > + * @item: The item to initialize
> > > + * @type: The subclass type
> > > + */
> > > +static inline void ttm_lru_item_init(struct ttm_lru_item *item,
> > > + enum ttm_lru_item_type
> > > type)
> > > +{
> > > + item->type = type;
> > > + INIT_LIST_HEAD(&item->link);
> > > +}
> > > +
> > > +static inline bool ttm_lru_item_is_res(const struct ttm_lru_item
> > > *item)
> > > +{
> > > + return item->type == TTM_LRU_RESOURCE;
> > > +}
> > > +
> > > struct ttm_resource_manager_func {
> > > /**
> > > * struct ttm_resource_manager_func member alloc
> > > @@ -217,9 +254,21 @@ struct ttm_resource {
> > > /**
> > > * @lru: Least recently used list, see
> > > &ttm_resource_manager.lru
> > > */
> > > - struct list_head lru;
> > > + struct ttm_lru_item lru;
> > > };
> > >
> > > +/**
> > > + * ttm_lru_item_to_res() - Downcast a struct ttm_lru_item to a
> > > struct ttm_resource
> > > + * @item: The struct ttm_lru_item to downcast
> > > + *
> > > + * Return: Pointer to the embedding struct ttm_resource
> > > + */
> > > +static inline struct ttm_resource *
> > > +ttm_lru_item_to_res(struct ttm_lru_item *item)
> > Pretty much everywhere in this series we have the following coding
> > pattern:
> >
> > if (ttm_lru_item_is_res(item))
> > do something with ttm_lru_item_to_res(item);
> >
> > Would it make more sense to squash these functions together with
> > only
> > ttm_lru_item_to_res which returns NULL if item is not
> > TTM_LRU_RESOURCE?
> >
> > The new pattern would be:
> >
> > res = ttm_lru_item_is_res(item)
> > if (res)
> > do something with res
> >
> > What do you think?
After looking into this, in the typical case this would actually amount
to
struct ttm_resource *res = ttm_lru_item_to_res(item)
if (res)
do_something_with_res()
So four lines instead of two and an extra variable. So I don't see the
immediate benefit. I can change if you guys insist, though
>
> I would even say we should put that filtering into the iterator.
>
> Nobody except the code which inserted the anchor into the LRU is
> interested in it.
That's true, and it's already part of the _next() iterator function.
However in those places where the iteration is open-coded it's still
present. Those functions are typically intended to drain the LRU list.
I could probably introduce a
struct ttm_resource *ttm_lru_first_res_or_null(struct
list_head *);
function to handle those cases, though.
/Thomas.
>
> Regards,
> Christian.
>
> >
> > Matt
> >
> > > +{
> > > + return container_of(item, struct ttm_resource, lru);
> > > +}
> > > +
> > > /**
> > > * struct ttm_resource_cursor
> > > *
> > > --
> > > 2.44.0
> > >
>
