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auth=pass smtp.mailfrom=craftfever@murena.io ARC-Seal: i=1; s=mail3; d=murena.io; t=1760347320; a=rsa-sha256; cv=none; b=PwxP0AJIGQ/zfae6OZPyxKRCEAvpNf8EfcnkrLjQIBKFO2tS2RnKuNHcH5drsPOS9Z1VhZ O7NVGyHPg8bPUnXFEb+uvNtlzDvXRUz/0yXFrSTpP5uJFD83/3kfXOcg9kbSZPUHwKwHjL I40Fy8Kl5ivXS/7kQUO8jMXV5qtZAzg= MIME-Version: 1.0 Date: Mon, 13 Oct 2025 09:22:00 +0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: craftfever@murena.io Message-ID: <020cf8de6e773bb78ba7614ef250129f11a63781@murena.io> TLS-Required: No Subject: [Regerssion] [KSM] KSM CPU overhead in 6.16+ kernel compared to <=6.15 versions ("folio_walk_start" kernel object overhead) To: akpm@linux-foundation.org, david@redhat.com, xu.xin16@zte.com.cn, chengming.zhou@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev X-Rspam-User: X-Rspamd-Queue-Id: EA67720009 X-Rspamd-Server: rspam02 X-Stat-Signature: zkabtz3zdook7d4qo3otaqd5uhhcxf3c X-HE-Tag: 1760347322-361149 X-HE-Meta: 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 ktPUkEXP ZYmAiT/SMSJ1RlrcIZzNqXpzBnvIKRdtXryA56AOni6sqHBWp63S4L+fwYe+j+70TrIL7BicsKihWyU4ALbfpZFefyujnGBBznOX5rsJraW4JfYHwvY1+dEgab5crA8M5+uNNgeIOQC/vlQKQhNs79E3pHJEPQmD2fFiFPPcottf5PkMdgrMvVgcrpEUJiKmhzm50QpXniFDa6QPwknI1YUNpCsxqjZ1Zk3rnNpNRAOiNVt/wqx5b4v7aJ9GJPWIt9lWK/rf/lgDEYHExJ1rPaDwH0Pp6XSKbyGZlhEyuGdGUQkZnPlfDjUDYRVYD9gfDhEE8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005989, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: I've posted about that problem already on bigzilla (#220599), but maintai= ners asked to post issues on maillist. The problem with freezes during KSM page scanning with certain processes = like Chromium with huge virtual memory size amount was fized in 6.17.1 co= mpared to 6.16.x/6.17, but problem with huge CPU overhead is present ther= e. Compared to Linux <=3D6.15, where the overhead is much lighter anad th= ere no much CPU consuming during KSM scanning, there is "folio_walk_start= " kernel object is present (which I reviewed with "perf top" command) tha= t is not present in versions <=3D6.15 during KSM work and which is in wor= k starting from Linux 6.16. This method very resource-consuming compared = to algorithm used in <=3D6.15 versions. Is there a kernel parameter to di= sable it or it needs more optimization? I'm using MemoryKSM setting in systemd in user@.service for KSM process m= erging and it very light on <=3D6.15 ver., but CPU consuming on 6.16+ (6.= 17.1 without freezes) due to reasons said above.