From nobody Thu Apr 9 20:05:52 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8712B3CF69E; Fri, 6 Mar 2026 15:29:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772810963; cv=none; b=leKjP6SllYLXznEOrpl7V7b37aRyRRM4PS7eFALq8RAMt9TN9l6NL7JeDyvHuFrGXrm1ivc3Ap8PtVaH5MZ1QZ+Ztt3PFHD3wghIGdJe50K0aqT729Eww2VfYh77xuWAK1j39zC3RBe3x7nu8ZsUL6LjVz4VwvsuRTKvdeNuWrE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772810963; c=relaxed/simple; bh=lNQhvpFnr2Kehya342ovbJrx9ImZU409SPVoAQ9GUWs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TRzokatqreTtRNgU/DG8+VN+szDgWg7KprgIZhzWqBMF/Xu4UrjSc1gY/RdWavk+5OvBD6GUjHWrp4HHxE5ERGqDJcKKpP82TD7IksxL2GD1+HmmzOJmlDJgkcdSDoESjq+1UQZIX2yjbQF9hDEUJvt2fF1jaUlvX18fFUnsDHo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jV8uMcTN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jV8uMcTN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42347C2BD00; Fri, 6 Mar 2026 15:29:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772810963; bh=lNQhvpFnr2Kehya342ovbJrx9ImZU409SPVoAQ9GUWs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jV8uMcTNRpQluGW6AZdtbiWhDl0ty9J1UACsJDbieFyAB/TuOa6BFeYza062Ckht/ yAX0Fff3ExGhQdexGdIhS8o3KmHnhudqZraQ2bgFlfj8ChnNp9T6lHRIowTahiHCtF wdtW5Y0zzcW5s7U1+saWdzNe6rOmmKRWDW1VaYXadzF6GpT43ZfmSr6KAqocnpsqmx gjwG1yDnm2Q68hk6i2aGz6Lt+xz5FM8U7+zhsm85mFmInuaACW5ljvr1HxdxzzWMZo sj+QnyOWBRTsvnPFNUk4w6CQKfl++7+5jyJFq7RR4QtJpimQxfRJYel6B852BuiXu0 vTX06q27i7eNQ== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 06/10] mm/damon/core: add damon_merge_regions_of() debug_sanity check Date: Fri, 6 Mar 2026 07:29:09 -0800 Message-ID: <20260306152914.86303-7-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260306152914.86303-1-sj@kernel.org> References: <20260306152914.86303-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" damon_merge_regions_of() should be called only after aggregation is finished and therefore each region's nr_accesses and nr_accesses_bp match. There were bugs that broke the assumption, during development of online DAMON parameter updates and monitoring results handling changes. Add a sanity check for that under CONFIG_DAMON_DEBUG_SANITY. Signed-off-by: SeongJae Park --- mm/damon/core.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 8a3738a17cdd9..93d1577b1ae07 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2505,6 +2505,20 @@ static void damon_merge_two_regions(struct damon_tar= get *t, damon_destroy_region(r, t); } =20 +#ifdef CONFIG_DAMON_DEBUG_SANITY +static void damon_verify_merge_regions_of(struct damon_region *r) +{ + WARN_ONCE(r->nr_accesses !=3D r->nr_accesses_bp / 10000, + "nr_accesses (%u) !=3D nr_accesses_bp (%u)\n", + r->nr_accesses, r->nr_accesses_bp); +} +#else +static void damon_verify_merge_regions_of(struct damon_region *r) +{ +} +#endif + + /* * Merge adjacent regions having similar access frequencies * @@ -2518,6 +2532,7 @@ static void damon_merge_regions_of(struct damon_targe= t *t, unsigned int thres, struct damon_region *r, *prev =3D NULL, *next; =20 damon_for_each_region_safe(r, next, t) { + damon_verify_merge_regions_of(r); if (abs(r->nr_accesses - r->last_nr_accesses) > thres) r->age =3D 0; else if ((r->nr_accesses =3D=3D 0) !=3D (r->last_nr_accesses =3D=3D 0)) --=20 2.47.3