[PATCH v4 2/4] drm/ttm: Use LRU hitches
Thomas Hellström
thomas.hellstrom at linux.intel.com
Mon Mar 11 13:04:59 UTC 2024
Hi! Thanks for reviewing.
On Fri, 2024-03-08 at 18:50 +0530, Somalapuram, Amaranath wrote:
>
> On 3/6/2024 12:31 PM, Thomas Hellström wrote:
> > Have iterators insert themselves into the list they are iterating
> > over using hitch list nodes. Since only the iterator owner
> > can remove these list nodes from the list, it's safe to unlock
> > the list and when continuing, use them as a starting point. Due to
> > the way LRU bumping works in TTM, newly added items will not be
> > missed, and bumped items will be iterated over a second time before
> > reaching the end of the list.
> >
> > The exception is list with bulk move sublists. When bumping a
> > sublist, a hitch that is part of that sublist will also be moved
> > and we might miss items if restarting from it. This will be
> > addressed in a later patch.
> >
> > v2:
> > - Updated ttm_resource_cursor_fini() documentation.
> >
> > Cc: Christian König <christian.koenig at amd.com>
> > Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
> > Cc: <dri-devel at lists.freedesktop.org>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > ---
> > drivers/gpu/drm/ttm/ttm_bo.c | 1 +
> > drivers/gpu/drm/ttm/ttm_device.c | 9 ++-
> > drivers/gpu/drm/ttm/ttm_resource.c | 94 ++++++++++++++++++++-----
> > -----
> > include/drm/ttm/ttm_resource.h | 16 +++--
> > 4 files changed, 82 insertions(+), 38 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> > b/drivers/gpu/drm/ttm/ttm_bo.c
> > index e059b1e1b13b..b6f75a0ff2e5 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -622,6 +622,7 @@ int ttm_mem_evict_first(struct ttm_device
> > *bdev,
> > if (locked)
> > dma_resv_unlock(res->bo->base.resv);
> > }
> > + ttm_resource_cursor_fini_locked(&cursor);
> >
> > if (!bo) {
> > if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
> > diff --git a/drivers/gpu/drm/ttm/ttm_device.c
> > b/drivers/gpu/drm/ttm/ttm_device.c
> > index f27406e851e5..e8a6a1dab669 100644
> > --- a/drivers/gpu/drm/ttm/ttm_device.c
> > +++ b/drivers/gpu/drm/ttm/ttm_device.c
> > @@ -169,12 +169,17 @@ int ttm_device_swapout(struct ttm_device
> > *bdev, struct ttm_operation_ctx *ctx,
> > num_pages = PFN_UP(bo->base.size);
> > ret = ttm_bo_swapout(bo, ctx, gfp_flags);
> > /* ttm_bo_swapout has dropped the lru_lock
> > */
> > - if (!ret)
> > + if (!ret) {
> > + ttm_resource_cursor_fini(&cursor);
>
> is spin_unlock(&bdev->lru_lock) missing ?
>
> > return num_pages;
> > - if (ret != -EBUSY)
> > + }
> > + if (ret != -EBUSY) {
> > + ttm_resource_cursor_fini(&cursor);
>
> is spin_unlock(&bdev->lru_lock) missing ?
The ttm_bo_swapout() function returns unlocked depending on the error
code. IIRC it only returns locked on -EBUSY. That is something we
hopefully can change when this series is in place.
/Thomas
>
> Regards,
> S.Amarnath
> > return ret;
> > + }
> > }
> > }
> > + ttm_resource_cursor_fini_locked(&cursor);
> > spin_unlock(&bdev->lru_lock);
> > return 0;
> > }
> > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > b/drivers/gpu/drm/ttm/ttm_resource.c
> > index ee1865f82cb4..971014fca10a 100644
> > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > @@ -32,6 +32,37 @@
> >
> > #include <drm/drm_util.h>
> >
> > +/**
> > + * ttm_resource_cursor_fini_locked() - Finalize the LRU list
> > cursor usage
> > + * @cursor: The struct ttm_resource_cursor to finalize.
> > + *
> > + * The function pulls the LRU list cursor off any lists it was
> > previusly
> > + * attached to. Needs to be called with the LRU lock held. The
> > function
> > + * can be called multiple times after eachother.
> > + */
> > +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_fini() - Finalize the LRU list cursor usage
> > + * @cursor: The struct ttm_resource_cursor to finalize.
> > + *
> > + * The function pulls the LRU list cursor off any lists it was
> > previusly
> > + * attached to. Needs to be called without the LRU list lock held.
> > The
> > + * function can be called multiple times after eachother.
> > + */
> > +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
> > +{
> > + spinlock_t *lru_lock = &cursor->man->bdev->lru_lock;
> > +
> > + spin_lock(lru_lock);
> > + ttm_resource_cursor_fini_locked(cursor);
> > + spin_unlock(lru_lock);
> > +}
> > +
> > /**
> > * ttm_lru_bulk_move_init - initialize a bulk move structure
> > * @bulk: the structure to init
> > @@ -483,62 +514,63 @@ void ttm_resource_manager_debug(struct
> > ttm_resource_manager *man,
> > EXPORT_SYMBOL(ttm_resource_manager_debug);
> >
> > /**
> > - * ttm_resource_manager_first
> > - *
> > - * @man: resource manager to iterate over
> > + * ttm_resource_manager_next() - Continue iterating over the
> > resource manager
> > + * resources
> > * @cursor: cursor to record the position
> > *
> > - * Returns the first resource from the resource manager.
> > + * Return: The next resource from the resource manager.
> > */
> > struct ttm_resource *
> > -ttm_resource_manager_first(struct ttm_resource_manager *man,
> > - struct ttm_resource_cursor *cursor)
> > +ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
> > {
> > + struct ttm_resource_manager *man = cursor->man;
> > 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(lru, &man->lru[cursor-
> > >priority], link) {
> > - if (ttm_lru_item_is_res(lru))
> > + do {
> > + lru = &cursor->hitch;
> > + list_for_each_entry_continue(lru, &man-
> > >lru[cursor->priority], link) {
> > + if (ttm_lru_item_is_res(lru)) {
> > + list_move(&cursor->hitch.link,
> > &lru->link);
> > return ttm_lru_item_to_res(lru);
> > + }
> > }
> >
> > + if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
> > + break;
> > +
> > + list_move(&cursor->hitch.link, &man->lru[cursor-
> > >priority]);
> > + } while (true);
> > +
> > + list_del_init(&cursor->hitch.link);
> > +
> > return NULL;
> > }
> >
> > /**
> > - * ttm_resource_manager_next
> > - *
> > + * ttm_resource_manager_first() - Start iterating over the
> > resources
> > + * of a resource manager
> > * @man: resource manager to iterate over
> > * @cursor: cursor to record the position
> > - * @res: the current resource pointer
> > *
> > - * Returns the next resource from the resource manager.
> > + * Initializes the cursor and starts iterating. When done
> > iterating,
> > + * the caller must explicitly call ttm_resource_cursor_fini().
> > + *
> > + * Return: The first resource from the resource manager.
> > */
> > struct ttm_resource *
> > -ttm_resource_manager_next(struct ttm_resource_manager *man,
> > - struct ttm_resource_cursor *cursor,
> > - struct ttm_resource *res)
> > +ttm_resource_manager_first(struct ttm_resource_manager *man,
> > + struct ttm_resource_cursor *cursor)
> > {
> > - struct ttm_lru_item *lru = &res->lru;
> > -
> > lockdep_assert_held(&man->bdev->lru_lock);
> >
> > - 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);
> > - }
> > + cursor->priority = 0;
> > + cursor->man = man;
> > + ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
> > + list_move(&cursor->hitch.link, &man->lru[cursor-
> > >priority]);
> >
> > - for (++cursor->priority; cursor->priority <
> > TTM_MAX_BO_PRIORITY;
> > - ++cursor->priority)
> > - 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;
> > + return ttm_resource_manager_next(cursor);
> > }
> >
> > static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter
> > *iter,
> > diff --git a/include/drm/ttm/ttm_resource.h
> > b/include/drm/ttm/ttm_resource.h
> > index cad8c5476198..b9043c183205 100644
> > --- a/include/drm/ttm/ttm_resource.h
> > +++ b/include/drm/ttm/ttm_resource.h
> > @@ -271,15 +271,23 @@ ttm_lru_item_to_res(struct ttm_lru_item
> > *item)
> >
> > /**
> > * 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
> > *
> > @@ -435,9 +443,7 @@ struct ttm_resource *
> > ttm_resource_manager_first(struct ttm_resource_manager *man,
> > struct ttm_resource_cursor *cursor);
> > struct ttm_resource *
> > -ttm_resource_manager_next(struct ttm_resource_manager *man,
> > - struct ttm_resource_cursor *cursor,
> > - struct ttm_resource *res);
> > +ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
> >
> > /**
> > * ttm_resource_manager_for_each_res - iterate over all resources
> > @@ -449,7 +455,7 @@ ttm_resource_manager_next(struct
> > ttm_resource_manager *man,
> > */
> > #define ttm_resource_manager_for_each_res(man, cursor,
> > res) \
> > for (res = ttm_resource_manager_first(man, cursor);
> > res; \
> > - res = ttm_resource_manager_next(man, cursor, res))
> > + res = ttm_resource_manager_next(cursor))
> >
> > struct ttm_kmap_iter *
> > ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
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