From mboxrd@z Thu Jan 1 00:00:00 1970 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 609D5202F71; Sun, 1 Mar 2026 16:42:33 +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=1772383353; cv=none; b=jZuqTp8rybdaGiekG3MHxVPlYt2MsUCe7FHhac5kabbXd+T2f+JkkYtSTBMB5rywRdcXdWGEtOaIhGx/wgnmen81EH8cAeuby9O3qJ82df1AARXcBujHiBOh8VnaFWln6FfktPFRoZjJziOdkXEKYRed4iz09RExoi4Z9vtkqWk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772383353; c=relaxed/simple; bh=2gPoW7S6UrtEjGc6IJ81tfoCTpZblLaI9E7KswG3ITU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rgUsxo220hk8uXLUYl+JSHNQEHgI9QX40lBS5vgWAUobUaSnHu0IFZauxjrSe9nWiwAlAm6LR1eWXdHzzm1Fj4jYaRbEA+OMJp/ePTyPfHtx9hhxjxQU6Qj+g5pBV2cEKRTTAd5i3QinG7MUb/AGavivp0WJB5E/DTJjCgwO4fc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Wnd70n6j; 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="Wnd70n6j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBF7DC116C6; Sun, 1 Mar 2026 16:42:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772383353; bh=2gPoW7S6UrtEjGc6IJ81tfoCTpZblLaI9E7KswG3ITU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Wnd70n6jiT0ymJ3bZwNy8tt0sM37n3DbyG9rBZ7/nDH0Xx01Rpu9ecDXBPcQrSwQH 8+pui6ei6kTqKPaMFYKOjbUVLcf7AzzlJ5ysP3ASBSfbP+Gz093exPm/ch2k/UxPxJ UiasMVnDPx2N6m64OSFAX6ympGAKUGikcLoaQ4z9/gvU5DfhE8o3ycHdfoDwI4xsYC EiL+G1gUgq4z3/meX3wghqQzPqdkAQMBgGZNIUoVqzgsLqhBHYkyU9D48mgDUm0VkJ UG5+O4WQza1TH/DTcTOjq+OE+Uo7j6lALf/9RF/MrPDF84xeyqhNBzX5Gh2EAmvRct RExOjJqdBLWLg== From: SeongJae Park To: SeongJae Park Cc: Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 06/10] mm/damon/core: add damon_merge_regions_of() debug_sanity check Date: Sun, 1 Mar 2026 08:42:25 -0800 Message-ID: <20260301164226.93108-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260221193629.19332-7-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sat, 21 Feb 2026 11:36:23 -0800 SeongJae Park wrote: > 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 | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 291a847a8c9bb..94be598cafef1 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -2545,6 +2545,22 @@ static void damon_merge_two_regions(struct damon_target *t, > damon_destroy_region(r, t); > } > > +#ifdef CONFIG_DAMON_DEBUG_SANITY > +static void damon_verify_merge_regions_of(struct damon_region *r) > +{ > + if (r->nr_accesses == r->nr_accesses_bp / 10000) > + return; > + pr_err("nr_accesses (%u) != nr_accesses_bp (%u)\n", > + r->nr_accesses, r->nr_accesses_bp); > + WARN_ONCE(); > +} > +#else > +static void damon_verify_merge_regions_of(struct damon_region *r) > +{ > +} > +#endif > + > + > /* > * Merge adjacent regions having similar access frequencies > * > @@ -2565,6 +2581,8 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, > else > r->age++; > > + damon_verify_merge_regions_of(r); > + This verification doesn't need to be here, after the above 'age' updates. I'll move this to the beginning of this scope in the next spin. > if (prev && prev->ar.end == r->ar.start && > abs(prev->nr_accesses - r->nr_accesses) <= thres && > damon_sz_region(prev) + damon_sz_region(r) <= sz_limit) > -- > 2.47.3 Thanks, SJ