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b=K5UY8Zvjp1eYY5r/rPrTFiHV8It0TmxUheywYjqhe7/5YTVYIAd1C95cYaKpBQk9G umZoZAk/ggenMZu5icE1KDY7FwZANvYhweISxsVS/BxQSzVOL75Ue9lV7vM9TyZtXp ESOCq7MeM/ZNpWRb6cxlSUlz6CeHYbU33ptg++H4WuxvyTZKsJLU1lNxeYikIZqJCM 1DBkPiV/0tVpCBelywdGNgrxQpIX3JohQDUsw6F6cwjf0YfgA3jlzRrksOj1UAYH6L NH2vvvQT2xPD6BWXkPKKtDJLlqLqN4XNlzlVtblE/Mu5Uhm2i+4h+HV24N269+vpy8 jJEFIHeikK8IA== From: SJ Park To: Andrew Morton Cc: SJ Park , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 03/18] mm/damon/core: always update ->last_nr_accesses for intervals change Date: Mon, 29 Jun 2026 21:07:56 -0700 Message-ID: <20260630040812.149729-4-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260630040812.149729-1-sj@kernel.org> References: <20260630040812.149729-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: frw49f44b5ks5cya8twdt8egdhkz7438 X-Rspamd-Queue-Id: C83B940009 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1782792505-926581 X-HE-Meta: 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 +nxmIYed g3ZoI8e0AuBrtWr7Iv/CIRYJK630Mosc6VS7qOg2d9vLKG+1d4jW97ijeeKb5PoCRVWqVaruabbVgPemyRviEQsrKIB/eApz6K1iUtzoIKnEWvR24P2tsmSkjJqj4Js27ZKnN6bo3qTSNtKAndSxxg1xzSIeIfp7PHqWtfQXR/bv921H/qPqTJq9DSm0ukrds1rD3vztpH7zoczEczG23JfNUzpC/sgvNBGrZo9ha43LQWHL8Xqpz5/aBaawmoZW/2gTtLG+juQmWVDcCo5swHK0rnA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Each iteration of kdamond_fn() main loop caches and use the next aggregation time (next_aggregation_sis) because it can be updated in the middle, inside kdamond_call(). If that happens, damon_update_monitoring_result() is called for scaling the access frequency information of each region according to the changed intervals. The function does not update damon_region->last_nr_accesses when it is at the end of the aggregation, because it will anyway be reset after the function is executed, in kdamond_reset_aggregated(). Let's suppose damon_nr_accesses_mvsum() is called with the not yet updated last_nr_accesses. It will use the fresh next_aggregation_sis in the context instead of the cached one, unlike kdamond_fn(). As a result, use of not updated last_nr_acceses with the updated next_aggregation_sis result in returning wrong value. There is no such damon_nr_accesses_nvsum() call at the moment, so this is no problem. It is planned to add such calls, though. Prevent the issue by updating last_nr_accesses always. This adds overhead, but that's fine because the overhead is not big, and it is anyway not a fast path. Signed-off-by: SJ Park --- mm/damon/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index c588f943080f9..669b701e50a7d 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -877,6 +877,8 @@ static void damon_update_monitoring_result(struct damon_region *r, struct damon_attrs *old_attrs, struct damon_attrs *new_attrs, bool aggregating) { + r->last_nr_accesses = damon_nr_accesses_for_new_attrs( + r->last_nr_accesses, old_attrs, new_attrs); if (!aggregating) { r->nr_accesses = damon_nr_accesses_for_new_attrs( r->nr_accesses, old_attrs, new_attrs); @@ -888,8 +890,6 @@ static void damon_update_monitoring_result(struct damon_region *r, * interval. In other words, make the status like * kdamond_reset_aggregated() is called. */ - r->last_nr_accesses = damon_nr_accesses_for_new_attrs( - r->last_nr_accesses, old_attrs, new_attrs); r->nr_accesses_bp = r->last_nr_accesses * 10000; r->nr_accesses = 0; } -- 2.47.3