6.6-stable review patch. If anyone has any objections, please let me know.
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From: Tvrtko Ursulin tvrtko.ursulin@igalia.com
[ Upstream commit eac21f8ebeb4f84d703cf41dc3f81d16fa9dc00a ]
Currently the TTM shrinker aborts shrinking as soon as it frees pages from any of the page order pools and by doing so it can fail to respect the freeing target which was configured by the shrinker core.
We use the wording "can fail" because the number of freed pages will depend on the presence of pages in the pools and the order of the pools on the LRU list. For example if there are no free pages in the high order pools the shrinker core may require multiple passes over the TTM shrinker before it will free the default target of 128 pages (assuming there are free pages in the low order pools). This inefficiency can be compounded by the pool LRU where multiple further calls into the TTM shrinker are required to end up looking at the pool with pages.
Improve this by never freeing less than the shrinker core has requested.
At the same time we start reporting the number of scanned pages (freed in this case), which prevents the core shrinker from giving up on the TTM shrinker too soon and moving on.
v2: * Simplify loop logic. (Christian) * Improve commit message.
Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@igalia.com Cc: Christian König christian.koenig@amd.com Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Reviewed-by: Christian König christian.koenig@amd.com Signed-off-by: Tvrtko Ursulin tursulin@ursulin.net Link: https://lore.kernel.org/r/20250603112750.34997-2-tvrtko.ursulin@igalia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/ttm/ttm_pool.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index 37c08fac7e7d..80ba34cabca3 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -615,7 +615,6 @@ void ttm_pool_fini(struct ttm_pool *pool) } EXPORT_SYMBOL(ttm_pool_fini);
-/* As long as pages are available make sure to release at least one */ static unsigned long ttm_pool_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc) { @@ -623,9 +622,12 @@ static unsigned long ttm_pool_shrinker_scan(struct shrinker *shrink,
do num_freed += ttm_pool_shrink(); - while (!num_freed && atomic_long_read(&allocated_pages)); + while (num_freed < sc->nr_to_scan && + atomic_long_read(&allocated_pages));
- return num_freed; + sc->nr_scanned = num_freed; + + return num_freed ?: SHRINK_STOP; }
/* Return the number of pages available or SHRINK_EMPTY if we have none */