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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: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2D898180002 X-Stat-Signature: 4m6bujinu9jrn5yuanzi9n1pd8oke3ut X-Rspam-User: X-HE-Tag: 1772383353-935630 X-HE-Meta: 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 Zeec6HSK 6n3AtqPAaqYl4x7ANwsZNKPjgaPTHIp5O3GxDVtQ8SadUcJKYEdVpdtc61oRnIjV/csf5McX8PIlx4r6kq59pJn1mF3w0En+y+Fsvl8vMfGpCt/y4lYzhooHLd4s4EBHev7NM5b/put1DnGy46eRDHRD4zO9PAi+bPo/WWYf5tBuXxWcc1DS8sojMOnZBz6yWsBNQQZm7ua44AVYTyOb9C2TYktKcDAMr1pJEPPHzu94MGHnvze70x02Qzi1cFYCyXO5Qt4WKv3TEVM/WDBQSVCEVzg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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