[PATCH v7 7/8] drm/ttm: Use the LRU walker for eviction
Thomas Hellström
thomas.hellstrom at linux.intel.com
Fri Jul 5 15:32:05 UTC 2024
Use the LRU walker for eviction. This helps
removing a lot of code with weird locking
semantics.
The functionality is slightly changed so that
when trylocked buffer objects are exhausted, we
continue to interleave walks with ticket-locks while
there is still progress made. The list walks are
not restarted in-between evictions.
Also provide a separate ttm_bo_evict_first()
function for its single user. The context of that
user allows sleeping dma_resv locks.
v6:
- Various cleanups suggested by Matthew Brost.
- Fix error return code of ttm_bo_evict_first(). (Matthew Brost)
- Fix an error check that was inverted. (Matthew Brost)
v7:
- Use s64 rather than long (Christian König)
- Early ttm_resource_cursor_fini() in ttm_bo_evict_first().
- Simplify check for bo_moved in ttm_bo_evict_first().
(Christian König)
- Don't evict pinned bos.
Cc: Christian König <christian.koenig at amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: <dri-devel at lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost at intel.com> #v6
---
drivers/gpu/drm/ttm/ttm_bo.c | 345 ++++++++++++-----------------
drivers/gpu/drm/ttm/ttm_resource.c | 21 +-
include/drm/ttm/ttm_bo.h | 8 +-
3 files changed, 143 insertions(+), 231 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index f4b2b2bea6cb..0131ec802066 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -224,80 +224,6 @@ static void ttm_bo_flush_all_fences(struct ttm_buffer_object *bo)
dma_resv_iter_end(&cursor);
}
-/**
- * ttm_bo_cleanup_refs
- * If bo idle, remove from lru lists, and unref.
- * If not idle, block if possible.
- *
- * Must be called with lru_lock and reservation held, this function
- * will drop the lru lock and optionally the reservation lock before returning.
- *
- * @bo: The buffer object to clean-up
- * @interruptible: Any sleeps should occur interruptibly.
- * @no_wait_gpu: Never wait for gpu. Return -EBUSY instead.
- * @unlock_resv: Unlock the reservation lock as well.
- */
-
-static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
- bool interruptible, bool no_wait_gpu,
- bool unlock_resv)
-{
- struct dma_resv *resv = &bo->base._resv;
- int ret;
-
- if (dma_resv_test_signaled(resv, DMA_RESV_USAGE_BOOKKEEP))
- ret = 0;
- else
- ret = -EBUSY;
-
- if (ret && !no_wait_gpu) {
- long lret;
-
- if (unlock_resv)
- dma_resv_unlock(bo->base.resv);
- spin_unlock(&bo->bdev->lru_lock);
-
- lret = dma_resv_wait_timeout(resv, DMA_RESV_USAGE_BOOKKEEP,
- interruptible,
- 30 * HZ);
-
- if (lret < 0)
- return lret;
- else if (lret == 0)
- return -EBUSY;
-
- spin_lock(&bo->bdev->lru_lock);
- if (unlock_resv && !dma_resv_trylock(bo->base.resv)) {
- /*
- * We raced, and lost, someone else holds the reservation now,
- * and is probably busy in ttm_bo_cleanup_memtype_use.
- *
- * Even if it's not the case, because we finished waiting any
- * delayed destruction would succeed, so just return success
- * here.
- */
- spin_unlock(&bo->bdev->lru_lock);
- return 0;
- }
- ret = 0;
- }
-
- if (ret) {
- if (unlock_resv)
- dma_resv_unlock(bo->base.resv);
- spin_unlock(&bo->bdev->lru_lock);
- return ret;
- }
-
- spin_unlock(&bo->bdev->lru_lock);
- ttm_bo_cleanup_memtype_use(bo);
-
- if (unlock_resv)
- dma_resv_unlock(bo->base.resv);
-
- return 0;
-}
-
/*
* Block for the dma_resv object to become idle, lock the buffer and clean up
* the resource and tt object.
@@ -505,151 +431,152 @@ bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
}
EXPORT_SYMBOL(ttm_bo_eviction_valuable);
-/*
- * Check the target bo is allowable to be evicted or swapout, including cases:
- *
- * a. if share same reservation object with ctx->resv, have assumption
- * reservation objects should already be locked, so not lock again and
- * return true directly when either the opreation allow_reserved_eviction
- * or the target bo already is in delayed free list;
+/**
+ * ttm_bo_evict_first() - Evict the first bo on the manager's LRU list.
+ * @bdev: The ttm device.
+ * @man: The manager whose bo to evict.
+ * @ctx: The TTM operation ctx governing the eviction.
*
- * b. Otherwise, trylock it.
+ * Return: 0 if successful or the resource disappeared. Negative error code on error.
*/
-static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
- struct ttm_operation_ctx *ctx,
- const struct ttm_place *place,
- bool *locked, bool *busy)
+int ttm_bo_evict_first(struct ttm_device *bdev, struct ttm_resource_manager *man,
+ struct ttm_operation_ctx *ctx)
{
- bool ret = false;
+ struct ttm_resource_cursor cursor;
+ struct ttm_buffer_object *bo;
+ struct ttm_resource *res;
+ unsigned int mem_type;
+ int ret = 0;
- if (bo->pin_count) {
- *locked = false;
- if (busy)
- *busy = false;
- return false;
+ spin_lock(&bdev->lru_lock);
+ res = ttm_resource_manager_first(man, &cursor);
+ ttm_resource_cursor_fini(&cursor);
+ if (!res) {
+ ret = -ENOENT;
+ goto out_no_ref;
}
+ bo = res->bo;
+ if (!ttm_bo_get_unless_zero(bo))
+ goto out_no_ref;
+ mem_type = res->mem_type;
+ spin_unlock(&bdev->lru_lock);
+ ret = ttm_bo_reserve(bo, ctx->interruptible, ctx->no_wait_gpu, NULL);
+ if (ret)
+ goto out_no_lock;
+ if (!bo->resource || bo->resource->mem_type != mem_type)
+ goto out_bo_moved;
- if (bo->base.resv == ctx->resv) {
- dma_resv_assert_held(bo->base.resv);
- if (ctx->allow_res_evict)
- ret = true;
- *locked = false;
- if (busy)
- *busy = false;
+ if (bo->deleted) {
+ ret = ttm_bo_wait_ctx(bo, ctx);
+ if (!ret)
+ ttm_bo_cleanup_memtype_use(bo);
} else {
- ret = dma_resv_trylock(bo->base.resv);
- *locked = ret;
- if (busy)
- *busy = !ret;
- }
-
- if (ret && place && (bo->resource->mem_type != place->mem_type ||
- !bo->bdev->funcs->eviction_valuable(bo, place))) {
- ret = false;
- if (*locked) {
- dma_resv_unlock(bo->base.resv);
- *locked = false;
- }
+ ret = ttm_bo_evict(bo, ctx);
}
+out_bo_moved:
+ dma_resv_unlock(bo->base.resv);
+out_no_lock:
+ ttm_bo_put(bo);
+ return ret;
+out_no_ref:
+ spin_unlock(&bdev->lru_lock);
return ret;
}
/**
- * ttm_mem_evict_wait_busy - wait for a busy BO to become available
- *
- * @busy_bo: BO which couldn't be locked with trylock
- * @ctx: operation context
- * @ticket: acquire ticket
- *
- * Try to lock a busy buffer object to avoid failing eviction.
+ * struct ttm_bo_evict_walk - Parameters for the evict walk.
*/
-static int ttm_mem_evict_wait_busy(struct ttm_buffer_object *busy_bo,
- struct ttm_operation_ctx *ctx,
- struct ww_acquire_ctx *ticket)
-{
- int r;
-
- if (!busy_bo || !ticket)
- return -EBUSY;
-
- if (ctx->interruptible)
- r = dma_resv_lock_interruptible(busy_bo->base.resv,
- ticket);
- else
- r = dma_resv_lock(busy_bo->base.resv, ticket);
-
- /*
- * TODO: It would be better to keep the BO locked until allocation is at
- * least tried one more time, but that would mean a much larger rework
- * of TTM.
- */
- if (!r)
- dma_resv_unlock(busy_bo->base.resv);
-
- return r == -EDEADLK ? -EBUSY : r;
-}
+struct ttm_bo_evict_walk {
+ /** @walk: The walk base parameters. */
+ struct ttm_lru_walk walk;
+ /** @place: The place passed to the resource allocation. */
+ const struct ttm_place *place;
+ /** @evictor: The buffer object we're trying to make room for. */
+ struct ttm_buffer_object *evictor;
+ /** @res: The allocated resource if any. */
+ struct ttm_resource **res;
+ /** @evicted: Number of successful evictions. */
+ unsigned long evicted;
+};
-int ttm_mem_evict_first(struct ttm_device *bdev,
- struct ttm_resource_manager *man,
- const struct ttm_place *place,
- struct ttm_operation_ctx *ctx,
- struct ww_acquire_ctx *ticket)
+static s64 ttm_bo_evict_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo)
{
- struct ttm_buffer_object *bo = NULL, *busy_bo = NULL;
- struct ttm_resource_cursor cursor;
- struct ttm_resource *res;
- bool locked = false;
- int ret;
+ struct ttm_bo_evict_walk *evict_walk =
+ container_of(walk, typeof(*evict_walk), walk);
+ s64 lret;
- spin_lock(&bdev->lru_lock);
- ttm_resource_manager_for_each_res(man, &cursor, res) {
- bool busy;
-
- if (!ttm_bo_evict_swapout_allowable(res->bo, ctx, place,
- &locked, &busy)) {
- if (busy && !busy_bo && ticket !=
- dma_resv_locking_ctx(res->bo->base.resv))
- busy_bo = res->bo;
- continue;
- }
+ if (bo->pin_count || !bo->bdev->funcs->eviction_valuable(bo, evict_walk->place))
+ return 0;
- if (ttm_bo_get_unless_zero(res->bo)) {
- bo = res->bo;
- break;
- }
- if (locked)
- dma_resv_unlock(res->bo->base.resv);
+ if (bo->deleted) {
+ lret = ttm_bo_wait_ctx(bo, walk->ctx);
+ if (!lret)
+ ttm_bo_cleanup_memtype_use(bo);
+ } else {
+ lret = ttm_bo_evict(bo, walk->ctx);
}
- ttm_resource_cursor_fini(&cursor);
- if (!bo) {
- if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
- busy_bo = NULL;
- spin_unlock(&bdev->lru_lock);
- ret = ttm_mem_evict_wait_busy(busy_bo, ctx, ticket);
- if (busy_bo)
- ttm_bo_put(busy_bo);
- return ret;
- }
+ if (lret)
+ goto out;
- if (bo->deleted) {
- ret = ttm_bo_cleanup_refs(bo, ctx->interruptible,
- ctx->no_wait_gpu, locked);
- ttm_bo_put(bo);
- return ret;
- }
+ evict_walk->evicted++;
+ if (evict_walk->res)
+ lret = ttm_resource_alloc(evict_walk->evictor, evict_walk->place,
+ evict_walk->res);
+ if (lret == 0)
+ return 1;
+out:
+ /* Errors that should terminate the walk. */
+ if (lret == -ENOSPC)
+ return -EBUSY;
- spin_unlock(&bdev->lru_lock);
+ return lret;
+}
- ret = ttm_bo_evict(bo, ctx);
- if (locked)
- ttm_bo_unreserve(bo);
- else
- ttm_bo_move_to_lru_tail_unlocked(bo);
+static const struct ttm_lru_walk_ops ttm_evict_walk_ops = {
+ .process_bo = ttm_bo_evict_cb,
+};
- ttm_bo_put(bo);
- return ret;
+static int ttm_bo_evict_alloc(struct ttm_device *bdev,
+ struct ttm_resource_manager *man,
+ const struct ttm_place *place,
+ struct ttm_buffer_object *evictor,
+ struct ttm_operation_ctx *ctx,
+ struct ww_acquire_ctx *ticket,
+ struct ttm_resource **res)
+{
+ struct ttm_bo_evict_walk evict_walk = {
+ .walk = {
+ .ops = &ttm_evict_walk_ops,
+ .ctx = ctx,
+ .ticket = ticket,
+ },
+ .place = place,
+ .evictor = evictor,
+ .res = res,
+ };
+ s64 lret;
+
+ evict_walk.walk.trylock_only = true;
+ lret = ttm_lru_walk_for_evict(&evict_walk.walk, bdev, man, 1);
+ if (lret || !ticket)
+ goto out;
+
+ /* If ticket-locking, repeat while making progress. */
+ evict_walk.walk.trylock_only = false;
+ do {
+ /* The walk may clear the evict_walk.walk.ticket field */
+ evict_walk.walk.ticket = ticket;
+ evict_walk.evicted = 0;
+ lret = ttm_lru_walk_for_evict(&evict_walk.walk, bdev, man, 1);
+ } while (!lret && evict_walk.evicted);
+out:
+ if (lret < 0)
+ return lret;
+ if (lret == 0)
+ return -EBUSY;
+ return 0;
}
/**
@@ -760,6 +687,7 @@ static int ttm_bo_alloc_resource(struct ttm_buffer_object *bo,
for (i = 0; i < placement->num_placement; ++i) {
const struct ttm_place *place = &placement->placement[i];
struct ttm_resource_manager *man;
+ bool may_evict;
man = ttm_manager_type(bdev, place->mem_type);
if (!man || !ttm_resource_manager_used(man))
@@ -769,22 +697,21 @@ static int ttm_bo_alloc_resource(struct ttm_buffer_object *bo,
TTM_PL_FLAG_FALLBACK))
continue;
- do {
- ret = ttm_resource_alloc(bo, place, res);
- if (unlikely(ret && ret != -ENOSPC))
+ may_evict = (force_space && place->mem_type != TTM_PL_SYSTEM);
+ ret = ttm_resource_alloc(bo, place, res);
+ if (ret) {
+ if (ret != -ENOSPC)
return ret;
- if (likely(!ret) || !force_space)
- break;
-
- ret = ttm_mem_evict_first(bdev, man, place, ctx,
- ticket);
- if (unlikely(ret == -EBUSY))
- break;
- if (unlikely(ret))
+ if (!may_evict)
+ continue;
+
+ ret = ttm_bo_evict_alloc(bdev, man, place, bo, ctx,
+ ticket, res);
+ if (ret == -EBUSY)
+ continue;
+ if (ret)
return ret;
- } while (1);
- if (ret)
- continue;
+ }
ret = ttm_bo_add_move_fence(bo, man, ctx->no_wait_gpu);
if (unlikely(ret)) {
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index b43d04a1dc91..6d764ba88aab 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -495,24 +495,11 @@ int ttm_resource_manager_evict_all(struct ttm_device *bdev,
};
struct dma_fence *fence;
int ret;
- unsigned i;
-
- /*
- * Can't use standard list traversal since we're unlocking.
- */
- spin_lock(&bdev->lru_lock);
- for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
- while (!list_empty(&man->lru[i])) {
- spin_unlock(&bdev->lru_lock);
- ret = ttm_mem_evict_first(bdev, man, NULL, &ctx,
- NULL);
- if (ret)
- return ret;
- spin_lock(&bdev->lru_lock);
- }
- }
- spin_unlock(&bdev->lru_lock);
+ do {
+ ret = ttm_bo_evict_first(bdev, man, &ctx);
+ cond_resched();
+ } while (!ret);
spin_lock(&man->move_lock);
fence = dma_fence_get(man->move);
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index eb2692de06b8..d1a732d56259 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -422,11 +422,9 @@ s64 ttm_bo_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
s64 target);
void ttm_bo_pin(struct ttm_buffer_object *bo);
void ttm_bo_unpin(struct ttm_buffer_object *bo);
-int ttm_mem_evict_first(struct ttm_device *bdev,
- struct ttm_resource_manager *man,
- const struct ttm_place *place,
- struct ttm_operation_ctx *ctx,
- struct ww_acquire_ctx *ticket);
+int ttm_bo_evict_first(struct ttm_device *bdev,
+ struct ttm_resource_manager *man,
+ struct ttm_operation_ctx *ctx);
vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
struct vm_fault *vmf);
vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
--
2.44.0
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