From: SeongJae Park <sj@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: SeongJae Park <sj@kernel.org>,
	damon@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: [PATCH 09/14] mm/damon/core: remove damon_verify_nr_regions()
Date: Fri, 22 May 2026 08:40:20 -0700	[thread overview]
Message-ID: <20260522154026.80546-10-sj@kernel.org> (raw)
In-Reply-To: <20260522154026.80546-1-sj@kernel.org>

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.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 9cde5b47b9585..265d51ade25bf 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;
 }
 
-- 
2.47.3

next prev parent reply	other threads:[~2026-05-22 15:40 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-05-22 15:40 [PATCH 00/14] mm/damon: minor improvements for code readability and tests SeongJae Park
2026-05-22 15:40 ` [PATCH 01/14] mm/damon/core: safely handle no region case in damon_set_regions() SeongJae Park
2026-05-22 16:18   ` sashiko-bot
2026-05-22 20:09     ` SeongJae Park
2026-05-22 15:40 ` [PATCH 02/14] mm/damon/core: do not use region out of a loop " SeongJae Park
2026-05-22 15:40 ` [PATCH 03/14] samples/damon/mtier: replace damon_add_region() with damon_set_regions() SeongJae Park
2026-05-22 15:40 ` [PATCH 04/14] mm/damon/tests/vaddr-kunit: " SeongJae Park
2026-05-22 15:40 ` [PATCH 05/14] mm/damon/core: hide damon_add_region() SeongJae Park
2026-05-22 15:40 ` [PATCH 06/14] mm/damon/core: hide damon_insert_region() SeongJae Park
2026-05-22 15:40 ` [PATCH 07/14] mm/damon/core: hide damon_destroy_region() SeongJae Park
2026-05-22 15:40 ` [PATCH 08/14] mm/damon/core: add kdamond_call() debug_sanity check SeongJae Park
2026-05-22 17:55   ` sashiko-bot
2026-05-22 20:11     ` SeongJae Park
2026-05-22 15:40 ` SeongJae Park [this message]
2026-05-22 15:40 ` [PATCH 10/14] mm/damon/tests/core-kunit: add damon_set_regions() test cases SeongJae Park
2026-05-22 15:40 ` [PATCH 11/14] selftests/damon/sysfs.py: stop kdamonds before failing SeongJae Park
2026-05-22 15:40 ` [PATCH 12/14] selftests/damon/sysfs.sh: test monitoring intervals goal dir SeongJae Park
2026-05-22 15:40 ` [PATCH 13/14] selftests/damon/sysfs.sh: test addr_unit file existence SeongJae Park
2026-05-22 15:40 ` [PATCH 14/14] selftests/damon/sysfs.sh: test pause " SeongJae Park
2026-05-22 20:13 ` [PATCH 00/14] mm/damon: minor improvements for code readability and tests SeongJae Park
2026-05-22 20:22   ` Andrew Morton

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