[PATCH v13 6/8] drm/ttm: Add helpers for shrinking
Thomas Hellström
thomas.hellstrom at linux.intel.com
Wed Nov 13 18:35:48 UTC 2024
Add a number of helpers for shrinking that access core TTM and
core MM functionality in a way that make them unsuitable for
driver open-coding.
v11:
- New patch (split off from previous) and additional helpers.
v13:
- Adapt to ttm_backup interface change.
- Take resource off LRU when backed up.
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost at intel.com> #v11
---
drivers/gpu/drm/ttm/ttm_bo_util.c | 107 +++++++++++++++++++++++++++++-
drivers/gpu/drm/ttm/ttm_tt.c | 29 ++++++++
include/drm/ttm/ttm_bo.h | 21 ++++++
include/drm/ttm/ttm_tt.h | 2 +
4 files changed, 158 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 0cac02a9764c..15cab9bda17f 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -28,7 +28,7 @@
/*
* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
*/
-
+#include <linux/swap.h>
#include <linux/vmalloc.h>
#include <drm/ttm/ttm_bo.h>
@@ -1052,3 +1052,108 @@ struct ttm_buffer_object *ttm_bo_lru_cursor_first(struct ttm_bo_lru_cursor *curs
return bo ? bo : ttm_bo_lru_cursor_next(curs);
}
EXPORT_SYMBOL(ttm_bo_lru_cursor_first);
+
+/**
+ * ttm_bo_shrink() - Helper to shrink a ttm buffer object.
+ * @ctx: The struct ttm_operation_ctx used for the shrinking operation.
+ * @bo: The buffer object.
+ * @flags: Flags governing the shrinking behaviour.
+ *
+ * The function uses the ttm_tt_back_up functionality to back up or
+ * purge a struct ttm_tt. If the bo is not in system, it's first
+ * moved there.
+ *
+ * Return: The number of pages shrunken or purged, or
+ * negative error code on failure.
+ */
+long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
+ const struct ttm_bo_shrink_flags flags)
+{
+ static const struct ttm_place sys_placement_flags = {
+ .fpfn = 0,
+ .lpfn = 0,
+ .mem_type = TTM_PL_SYSTEM,
+ .flags = 0,
+ };
+ static struct ttm_placement sys_placement = {
+ .num_placement = 1,
+ .placement = &sys_placement_flags,
+ };
+ struct ttm_tt *tt = bo->ttm;
+ long lret;
+
+ dma_resv_assert_held(bo->base.resv);
+
+ if (flags.allow_move && bo->resource->mem_type != TTM_PL_SYSTEM) {
+ int ret = ttm_bo_validate(bo, &sys_placement, ctx);
+
+ /* Consider -ENOMEM and -ENOSPC non-fatal. */
+ if (ret) {
+ if (ret == -ENOMEM || ret == -ENOSPC)
+ ret = -EBUSY;
+ return ret;
+ }
+ }
+
+ ttm_bo_unmap_virtual(bo);
+ lret = ttm_bo_wait_ctx(bo, ctx);
+ if (lret < 0)
+ return lret;
+
+ if (bo->bulk_move) {
+ spin_lock(&bo->bdev->lru_lock);
+ ttm_resource_del_bulk_move(bo->resource, bo);
+ spin_unlock(&bo->bdev->lru_lock);
+ }
+
+ lret = ttm_tt_backup(bo->bdev, tt, (struct ttm_backup_flags)
+ {.purge = flags.purge,
+ .writeback = flags.writeback});
+
+ if (lret <= 0 && bo->bulk_move) {
+ spin_lock(&bo->bdev->lru_lock);
+ ttm_resource_add_bulk_move(bo->resource, bo);
+ spin_unlock(&bo->bdev->lru_lock);
+ }
+
+ if (lret < 0 && lret != -EINTR)
+ return -EBUSY;
+
+ return lret;
+}
+EXPORT_SYMBOL(ttm_bo_shrink);
+
+/**
+ * ttm_bo_shrink_suitable() - Whether a bo is suitable for shinking
+ * @ctx: The struct ttm_operation_ctx governing the shrinking.
+ * @bo: The candidate for shrinking.
+ *
+ * Check whether the object, given the information available to TTM,
+ * is suitable for shinking, This function can and should be used
+ * before attempting to shrink an object.
+ *
+ * Return: true if suitable. false if not.
+ */
+bool ttm_bo_shrink_suitable(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx)
+{
+ return bo->ttm && ttm_tt_is_populated(bo->ttm) && !bo->pin_count &&
+ (!ctx->no_wait_gpu ||
+ dma_resv_test_signaled(bo->base.resv, DMA_RESV_USAGE_BOOKKEEP));
+}
+EXPORT_SYMBOL(ttm_bo_shrink_suitable);
+
+/**
+ * ttm_bo_shrink_avoid_wait() - Whether to avoid waiting for GPU
+ * during shrinking
+ *
+ * In some situations, like direct reclaim, waiting (in particular gpu waiting)
+ * should be avoided since it may stall a system that could otherwise make progress
+ * shrinking something else less time consuming.
+ *
+ * Return: true if gpu waiting should be avoided, false if not.
+ */
+bool ttm_bo_shrink_avoid_wait(void)
+{
+ return !current_is_kswapd();
+}
+EXPORT_SYMBOL(ttm_bo_shrink_avoid_wait);
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index dd4eabe4ad79..85057380480b 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -514,3 +514,32 @@ unsigned long ttm_tt_pages_limit(void)
return ttm_pages_limit;
}
EXPORT_SYMBOL(ttm_tt_pages_limit);
+
+/**
+ * ttm_tt_setup_backup() - Allocate and assign a backup structure for a ttm_tt
+ * @tt: The ttm_tt for wich to allocate and assign a backup structure.
+ *
+ * Assign a backup structure to be used for tt backup. This should
+ * typically be done at bo creation, to avoid allocations at shrinking
+ * time.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int ttm_tt_setup_backup(struct ttm_tt *tt)
+{
+ struct ttm_backup *backup =
+ ttm_backup_shmem_create(((loff_t)tt->num_pages) << PAGE_SHIFT);
+
+ if (WARN_ON_ONCE(!(tt->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE)))
+ return -EINVAL;
+
+ if (IS_ERR(backup))
+ return PTR_ERR(backup);
+
+ if (tt->backup)
+ ttm_backup_fini(tt->backup);
+
+ tt->backup = backup;
+ return 0;
+}
+EXPORT_SYMBOL(ttm_tt_setup_backup);
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index 17d5ee049a8e..1abf2d8eb72c 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -225,6 +225,27 @@ struct ttm_lru_walk {
s64 ttm_lru_walk_for_evict(struct ttm_lru_walk *walk, struct ttm_device *bdev,
struct ttm_resource_manager *man, s64 target);
+/**
+ * struct ttm_bo_shrink_flags - flags to govern the bo shrinking behaviour
+ * @purge: Purge the content rather than backing it up.
+ * @writeback: Attempt to immediately write content to swap space.
+ * @allow_move: Allow moving to system before shrinking. This is typically
+ * not desired for zombie- or ghost objects (with zombie object meaning
+ * objects with a zero gem object refcount)
+ */
+struct ttm_bo_shrink_flags {
+ u32 purge : 1;
+ u32 writeback : 1;
+ u32 allow_move : 1;
+};
+
+long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
+ const struct ttm_bo_shrink_flags flags);
+
+bool ttm_bo_shrink_suitable(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx);
+
+bool ttm_bo_shrink_avoid_wait(void);
+
/**
* ttm_bo_get - reference a struct ttm_buffer_object
*
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 6ca2fc7b2a26..01752806cfbd 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -265,6 +265,8 @@ struct ttm_backup_flags {
long ttm_tt_backup(struct ttm_device *bdev, struct ttm_tt *tt,
const struct ttm_backup_flags flags);
+int ttm_tt_setup_backup(struct ttm_tt *tt);
+
#if IS_ENABLED(CONFIG_AGP)
#include <linux/agp_backend.h>
--
2.46.2
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