When __ttm_pool_alloc() fails to allocate a chunk at the device's beneficial order and falls back to a smaller order, the object ends up backed by a sub-optimal set of pages. Nothing currently records this, so a driver has no way to know an object would benefit from being re-backed with beneficial-order pages later.
Add TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED to struct ttm_tt page_flags, cleared at the start of every fresh allocation (in both ttm_pool_alloc() and ttm_pool_restore_and_alloc()). Set it in __ttm_pool_alloc() when an allocation at exactly the beneficial order fails before dropping to a lower order. Drivers can use this hint to queue the buffer object for later defragmentation. Cc: Carlos Santa <[email protected]> Cc: Ryan Neph <[email protected]> Cc: Christian Koenig <[email protected]> Cc: Huang Rui <[email protected]> Cc: Matthew Auld <[email protected]> Cc: Maarten Lankhorst <[email protected]> Cc: Maxime Ripard <[email protected]> Cc: Thomas Zimmermann <[email protected]> Cc: David Airlie <[email protected]> Cc: Simona Vetter <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Thomas Hellström <[email protected]> Assisted-by: GitHub_Copilot:claude-opus-4.8 Signed-off-by: Matthew Brost <[email protected]> --- drivers/gpu/drm/ttm/ttm_pool.c | 13 +++++++++++++ include/drm/ttm/ttm_tt.h | 24 +++++++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index d34592d4dbc7..370d991c9882 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -796,6 +796,7 @@ static int __ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt, struct ttm_pool_alloc_state *alloc, struct ttm_pool_tt_restore *restore) { + const unsigned int beneficial_order = ttm_pool_beneficial_order(pool); enum ttm_caching page_caching; gfp_t gfp_flags = GFP_USER; pgoff_t caching_divide; @@ -846,6 +847,16 @@ static int __ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt, /* If that fails, lower the order if possible and retry. */ if (!p) { if (order) { + /* + * Failing to allocate at the device's beneficial + * order means we are about to back this object + * with a sub-optimal (smaller order) set of + * pages. Record it so the driver can later try to + * defragment the object back to beneficial order. + */ + if (beneficial_order && order == beneficial_order) + tt->page_flags |= + TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED; --order; page_caching = tt->caching; allow_pools = true; @@ -910,6 +921,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt, if (WARN_ON(ttm_tt_is_backed_up(tt))) return -EINVAL; + tt->page_flags &= ~TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED; ttm_pool_alloc_state_init(tt, &alloc); return __ttm_pool_alloc(pool, tt, ctx, &alloc, NULL); @@ -942,6 +954,7 @@ int ttm_pool_restore_and_alloc(struct ttm_pool *pool, struct ttm_tt *tt, if (!restore) { gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; + tt->page_flags &= ~TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED; ttm_pool_alloc_state_init(tt, &alloc); if (ctx->gfp_retry_mayfail) gfp |= __GFP_RETRY_MAYFAIL; diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h index 406437ad674b..ce7533677d77 100644 --- a/include/drm/ttm/ttm_tt.h +++ b/include/drm/ttm/ttm_tt.h @@ -90,6 +90,14 @@ struct ttm_tt { * TTM_TT_FLAG_BACKED_UP: TTM internal only. This is set if the * struct ttm_tt has been (possibly partially) backed up. * + * TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED: Set by the TTM pool allocator + * when at least one chunk that could have been allocated at the pool's + * beneficial order had to fall back to a smaller order. This indicates + * that a sub-optimal set of pages was chosen for this object, and can + * be used by drivers to queue the buffer object for later + * defragmentation. Drivers should access this via the + * ttm_tt_is_beneficial_order_failed() helper. + * * TTM_TT_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE. This is * set by TTM after ttm_tt_populate() has successfully returned, and is * then unset when TTM calls ttm_tt_unpopulate(). @@ -101,8 +109,9 @@ struct ttm_tt { #define TTM_TT_FLAG_EXTERNAL_MAPPABLE BIT(3) #define TTM_TT_FLAG_DECRYPTED BIT(4) #define TTM_TT_FLAG_BACKED_UP BIT(5) +#define TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED BIT(6) -#define TTM_TT_FLAG_PRIV_POPULATED BIT(6) +#define TTM_TT_FLAG_PRIV_POPULATED BIT(7) uint32_t page_flags; /** @num_pages: Number of pages in the page array. */ uint32_t num_pages; @@ -179,6 +188,19 @@ static inline void ttm_tt_clear_backed_up(struct ttm_tt *tt) tt->page_flags &= ~TTM_TT_FLAG_BACKED_UP; } +/** + * ttm_tt_is_beneficial_order_failed() - Whether the tt is backed at a + * sub-optimal page order + * @tt: The struct ttm_tt. + * + * Return: true if the pool allocator had to fall back below the pool's + * beneficial order when backing this tt, false otherwise. + */ +static inline bool ttm_tt_is_beneficial_order_failed(const struct ttm_tt *tt) +{ + return tt->page_flags & TTM_TT_FLAG_BENEFICIAL_ORDER_FAILED; +} + /** * ttm_tt_create * -- 2.34.1
