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b=nxM200Xrc4NknLj1gtWX+oV2pwtyTatyhS2H1Vlz9g9OF2Tu8mzvB2FG34FF13Xq7 6jVSvEYjp7ph2Eb91fkCS3MOlYFFv2YHpbRZ5bdoNcdYqD4O3vtywWlyQW7Qc+lheO jLPvKkIU15UEO4EIh7ZsZd6MFcTvJ0zTjPFEwXbyTht3JDWnXSzEEUViFNFIeOnwT4 //a421l2H+W6jOTmRAhCAU4LpTUgtTSaIJvDDc2Stwb+CDftA7hyIf/SOF4A7IGBJL CDRosNOe+GaedyvylnHuwXVnX02mCbOQ+t2JI1D5LBvO0nckzK466iiCimykr3XB6E IJrcr8pKQJy9w== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joshua Hahn Subject: [PATCH v2 1/5] mm/damon/core: reset age if nr_accesses changes between non-zero and zero Date: Mon, 15 Sep 2025 20:23:35 -0700 Message-Id: <20250916032339.115817-2-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250916032339.115817-1-sj@kernel.org> References: <20250916032339.115817-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 543221C0006 X-Stat-Signature: 3hc94a9k1as9so6yezxoec9s48qu36qf X-Rspam-User: X-HE-Tag: 1757993029-480781 X-HE-Meta: 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 rTw8wFGk LTiyxiKaisCfPZeNL/ZCqg/GHDb5ocp8NkaS5465qmmyEkPgTmWYgSy/MWy1DVY01UTm9K3mi72yreoGsKSGscVhIAOzXI2vzjwEgRGzDaAsQhtW+ih9jqzbthXK9ZAWcxTPxONIjrtayrHUCsX5bcFXk40/nNzhG2UYNzzjhG5HnYn8eFHVZtbomhKqwsp2NIU7VmskygyKTb6wUwF9wDLpKaFVoSYQJjfN9uIpg/9XU14IRCVzrpHs9XEEd6mH1DS4rW9cpVvqWXlNkWVS3mQOJwiQOfkPWqaMqg5XfvNTdInY9GOHUPTrXaEQ6Ru0OlnYpQOIZql/b+stcFCKtvE7+rTEDvBT3pxh5MXi/az86sMdUWH85eQhJcA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: DAMON resets the age of a region if its nr_accesses value has significantly changed. Specifically, the threshold is calculated as 20% of largest nr_accesses of the current snapshot. This means that regions changing the nr_accesses from zero to small non-zero value or from a small non-zero value to zero will keep the age. Since many users treat zero nr_accesses regions special, this can be confusing. Kernel code including DAMOS' regions priority calculation and DAMON_STAT's idle time calculation also treat zero nr_accesses regions special. Make it unconfusing by resetting the age when the nr_accesses changes between zero and a non-zero value. Signed-off-by: SeongJae Park Reviewed-by: Joshua Hahn --- mm/damon/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index be5942435d78..ff2c6bb30621 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2261,6 +2261,8 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, damon_for_each_region_safe(r, next, t) { if (abs(r->nr_accesses - r->last_nr_accesses) > thres) r->age = 0; + else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0)) + r->age = 0; else r->age++; -- 2.39.5