From b8db646fe9a77845c37680ca416847ced5763c06 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Fri, 22 May 2026 08:40:20 -0700 Subject: [PATCH] mm/damon/core: remove damon_verify_nr_regions() When CONFIG_DAMON_DEBUG_SANITY is enabled, damon_verify_nr_regions() is called for each damon_nr_regions() invocation. damon_veify_nr_regions() iterates all regions. damon_nr_regions() is called for each region in kdamond_reset_aggregated() and damos_apply_scheme(). Hence it imposes O(n**2) overhead where n is the number of regions. Though the verification is enabled only under DAMON_DEBUG_SANITY, which is not for production use cases, it could be too high overhead. Meanwhile, damon_verify_ctx() is doing the damon_nr_regions() test. Because damon_verify_ctx() is called for each kdamond_call(), the test coverage from damon_verify_ctx() could be sufficient. Remove damon_nr_regions() verification. Link: https://lore.kernel.org/20260522154026.80546-10-sj@kernel.org Signed-off-by: SeongJae Park Cc: Brendan Higgins Cc: Shuah Khan Signed-off-by: Andrew Morton --- mm/damon/core.c | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 00e2997524ec..b33920873871 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -686,27 +686,8 @@ void damon_destroy_target(struct damon_target *t, struct damon_ctx *ctx) damon_free_target(t); } -#ifdef CONFIG_DAMON_DEBUG_SANITY -static void damon_verify_nr_regions(struct damon_target *t) -{ - struct damon_region *r; - unsigned int count = 0; - - damon_for_each_region(r, t) - count++; - WARN_ONCE(count != t->nr_regions, "t->nr_regions (%u) != count (%u)\n", - t->nr_regions, count); -} -#else -static void damon_verify_nr_regions(struct damon_target *t) -{ -} -#endif - unsigned int damon_nr_regions(struct damon_target *t) { - damon_verify_nr_regions(t); - return t->nr_regions; }