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b=l9J6Lw8PFf0Qbwatxu+AJWYvWKkEtVP5XYWvNymlcl8IwFuA2UcGFVLwvH1EKR+VZ F5qknpWvt/3eXbHDXbH+R2eSXv0QQffh9mm/DV/E5/QPbTaX+Td/P7D0a8Fx4XEwvV pZPfMxM7QstlHKnPyFIyWUFEQIwz+RYp17E3XvG2sOsLyOWcsBPF+cagHo9rvsvDgi 9Jec2A0StZgJH8A0iDTCzb4WpLs4dFOGBR++W1mEXXoXnfAWZgTSokf/zXBOQsMYgP l2AXGAQr83dV13fdpHw4lxaYPMaffvfqIgYGSB1WrQGzrUCrjN8ycffAmIA2u2mwzl LuFlt/DPYR91Q== From: SJ Park To: SJ Park Cc: Liew Rui Yan , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/core: fix unconditionally skip last region Date: Sun, 30 Aug 2026 11:19:18 -0700 Message-ID: <20260830181918.105052-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260830181445.104859-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 410FC80002 X-Stat-Signature: 6hpxqyzip788k96i1hgrcsmfx5nzx9i1 X-HE-Tag: 1788113967-897692 X-HE-Meta: U2FsdGVkX19YLXjsqdGx0guyGPfNeGziPxPg0XR2rLXJcosBHLxClRIli194r2dFfR0mVZ1+GLXUErbqBhtmcucHR775WQ1HwI0O1J4ur6FGF+gZWdcYlKtxoQDLGyRQ9DJdBHaAFbkiF9JrGMTx3Zcektd7HcP/aT4X/TNYTqXLKZR23Ix9pAz7Bo23m2lwbLGbZ9vqgM1KZ0S/ADcYOOL4MUmrNkRFWmkLZvSEIfsKyjPUuOnv7NDfGX5XYHFBaRYl8ZNryxjF7taruyFkYEzluw4mK9I7YJfAOpH+lJAsVVsVbVrYkWdv9p/sObK8VW3csPPa3ZyEr/2B2A7dpcZVd2B54VTk0MFWJVJ/Rq88yZzBcTQgds7T4ekeSUFfDPVGcC85OTzqB1l1wlzD1zGs5gkJ6jURAfpDqmaDYjdFR5FFQc9vqmYrwon60+/dhXfO1itCfgFhEp5H6PMxJBAZQQvRhLCzmGYNgwGOSubXIc3VwMkV0Kajq/+whNumuTXMNMS3h8emjV1TwE5lLhPENqijapNQRWToEi/D8eSmAj5kjnFirEv0Y2iberXB+ZEzQzDxLQ2Mm9xAGy7U72DgtbPBiXMRA8Vx/XcPMhjv7CBr0EiJNEkAb7sENr6qsLDTsYG3gFBRAGJGruDME+XLdRolohieZsR/LTI4ZZeWeChfWI+/H0x3aeIF38vZnZFvWTj5B5rkuxCigIyLoGrxZER2epDLSDtCRmBIrywaisK4mYEu9KQSNdxPnBi9Xc5sEmYP8XR15yZqeKy7VvnBI/vlbTYYwBGWZjODrq87rtqyDfWxGNjfRmYlsn5qzFeCaK49ySfEVTB8r5bCIfA2MTBQCCpVYuEXyzCdUqqE2wAfnl+N6cUc8pB1rVcXd12DxpDjpwaCvle1M2U9FHPIV750FlOOaA/gigsX9sqfkw32iBDbLsdKxwUXFOEfsodIC6e+0Toj4apyQbw CYMQe43J KJX8XOppI3B29/1XOod5O+lrBkQUkX6VJ4KbFRlSkjy0WAJROgGAXBsw5TwQS5fDNgfEc2vmTxjDM16nZpdipqi71qLJpp+DGRFQ4yTykdLIkrBY1rGLDO4ydM/8orDQ7Kb+l+lkVC2jqtOex+ju3RO9wzIqvec+aXFV/qeVLWsBJbYQ9z54HfHiL+y3C8EmPilG5e3BipM3bZRF4wRqDtwXvoeoKG9fcQJPI0rbYvAmkZ5a9+XpkKAN4Kuq9q8cqu90J3yBlM9DF1buH5IgZOTU2+A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 30 Aug 2026 11:14:52 -0700 SJ Park wrote: > On Sun, 30 Aug 2026 14:31:50 +0800 Liew Rui Yan wrote: > > > Once quota set, the charge_{target,addr}_from unconditionally skips and > > resets at the last region of the tracked target, so the last region can > > be skipped even when it has not been processed. > > > > Example: > > > > 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). > > 2. Quota is configured to process only 100 bytes per window. > > 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, > > addr}_from is saved at (Target, 100). > > 4. Window 2: The loop reaches R2. Because R2 is > > damon_last_region(t), the old code unconditionally returns true, > > skipping R2 entirely and resetting the charge_{target,addr}_from. > > > > Result: R2 is permanently skipped even though it has never been > > processed. > > > > However, it is important to note that this is a very minor issue. This > > is because it is triggered only when the previous window saved/kept > > charge_{target,addr}_from, and in the next window, all regions except > > the last region were skipped by damos_skip_charged_region(). > > > > Fix this by only resets the charge_{target,addr}_from when last region > > is reached, only skips when it applied or cannot split. > > Looks good to me! > > > > > Fixes: 50585192bc2e ("mm/damon/schemes: skip already charged targets and regions") > > Cc: # v5.16.x > > Signed-off-by: Liew Rui Yan > > Reviewed-by: SJ Park This patch is applied to damon/next [1] tree. If this patch is not added to mm.git in short term (~1 week?), I will ask mm.git maintainer (Andrew Morton) to pick this. So, no action from your side is needed for now. If it seems I also forgot doing that or you cannot wait for my action, please feel free to directly ask that to Andrew. [1] https://origin.kernel.org/doc/html/latest/mm/damon/maintainer-profile.html#scm-trees Thanks, SJ [...]