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Tue, 7 Jul 2026 10:33:04 +0800 (CST) Received: from kwepemr500001.china.huawei.com (unknown [7.202.194.229]) by mail.maildlp.com (Postfix) with ESMTPS id 661D04048B; Tue, 7 Jul 2026 10:42:16 +0800 (CST) Received: from [10.174.178.9] (10.174.178.9) by kwepemr500001.china.huawei.com (7.202.194.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 7 Jul 2026 10:42:15 +0800 Message-ID: <3aa50eea-ad23-4b19-9b31-a111dd5efb71@huawei.com> Date: Tue, 7 Jul 2026 10:42:14 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs/proc/task_mmu: count KSM-placed zero pages in smaps To: "David Hildenbrand (Arm)" , , , , , , , , , , CC: , References: <20260706121323.1149847-1-tujinjiang@huawei.com> <6ef49a9f-af0c-4bce-8402-16926424ea7a@kernel.org> From: Jinjiang Tu In-Reply-To: <6ef49a9f-af0c-4bce-8402-16926424ea7a@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.9] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 14A0D1C0002 X-Stat-Signature: t83dp8y1uaswjsimmzk1nzysrni1r7gf X-HE-Tag: 1783392140-874168 X-HE-Meta: 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 SjMVONsP 4fkEdX2IOpP4YpW0wmjIk8zcH2KG/bqj41qiVQX3AR1iRg0tuXHWyNy+6ngBH0VA0tmfxelcEjbgUdTK9AuRaB0fItZXY4ikHDhDvY/vJzUgNcgbFbdEddlV1q3v+QiZHUfzC9Vv4plt9zYnP4OL/CRt8u2HUETiYPffJSwsq/s01ZyFRxQmTKcf5hSaPtkqzmYWlcybuabARwTW6qx4lT7vVc8V6TL9Nfd2oyEHr7w7aEsdxky50YwMdec7x7RfRekWUH2WBPguOdUFBX3hboC2Meim0srUq6cKv1mw/1YYjwlhol4eXAbkgiJXxyuFVZhJHWMVTrHdeBqO3NF8g3poiTjlcShHJrj2fLlwy/dwhrxdbn3aEDHxdWOic3tr/RmhzjG+v7LPU7fs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/7/6 21:40, David Hildenbrand (Arm) 写道: > On 7/6/26 14:13, Jinjiang Tu wrote: >> When KSM deduplicates a page to the kernel zero page (i.e. when >> /sys/kernel/mm/ksm/use_zero_pages=1), it places a zero PTE with the dirty >> bit set. vm_normal_page() returns NULL for such PTEs, so smaps_pte_entry() >> bails out before reaching smaps_account() and these pages are never counted >> into mss->ksm. As a result /proc//smaps and smaps_rollup report a KSM >> value of 0 even though the region is fully merged. >> >> Count KSM-placed zero pages directly in smaps_pte_entry() using >> is_ksm_zero_pte(). > Hm. > > We do expose "ksm_zero_pages" in /proc//ksm_stat for calculating the KSM > profit. > > Why would we want to expose it here as KSM pages? I wasanalyzing the KSM profit of a process comes from which VMAs. However, smaps does not include the savings from ksm_zero_pages, make me fail to analyze. > An application will notice the difference between "zeropage enabled vs. > disabled" either way because we'll also not account zerpages towards e.g., > "Anonymous". > > So faking that something consumes memory when it actually doesn't consume memory > is wrong?