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b=I0Kfdsgpt2MNBf64t7Qf9F2ffnbma9jiMHAcZ+1Y0aUTT06CV7cZgafPnY7haTtAb vKD1qp443An/6+T8qahH+kSL2VEn2AtcwHENoXttNwdmypQLLH2+SM6KkjSfnsICRC dFLROykYYCG++15ZPcEcxiJsNO3YswU1RDcPeIMTQJsLWuWlQh8kJWpYH7oLz5izXZ q7oue+qXoY4JihTk3nKrJmGnyJCDGH9P9PxrlkebEa+17LNZArtuRK8Ex0EQwpcUzu qBShWVzolwP3xvc5Z/TFBWmGmGcKzMOPPMGiSd2V2UMBmGP7MbeAAL3/aruLgsktLH fchjhvFkNvhTw== Message-ID: <1da189ad-a7f6-42fa-a1ff-a26cc5e5c563@kernel.org> Date: Tue, 25 Aug 2026 19:34:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v1 2/3] mm/migrate.c: Prevent folio splitting from interacting with KSM To: Nico Pache Cc: Usama Arif , Zi Yan , ljs@kernel.org, xu.xin16@zte.com.cn, linux-kernel@vger.kernel.org, linux-mm@kvack.org, usamaarif642@gmail.com, yuzhao@google.com, aarcange@redhat.com, akpm@linux-foundation.org, chengming.zhou@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com References: <18102ABA-0D8E-4DA0-AC30-544E34E445D5@nvidia.com> <20260609172719.803537-1-usama.arif@linux.dev> <0b268070-95d2-45bd-aea3-56cefe01dc8c@kernel.org> <004bdc87-8c8e-44f8-93c3-1ae0a47051a9@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E8B82140006 X-Stat-Signature: homoiiqdoer44csobaz8texxsknpx6b7 X-HE-Tag: 1787679287-70360 X-HE-Meta: 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 ZJYR9eYB AO8cHROdBVki0MhepEgRy14EBBX2meMBNJ6ard5IDDS3AgP7B0Eth74COjX9m6tonHbokgb8U+DKxZDbmUC2Djy3opD9Bhk6eocCF0OxAKF8Ok7PTPqwrDP0gShJol2f63SxZbae4gi5jGE2CkTG1zOMVGjTglYBpTbEr7lkMNeQG1NXrFVr6/NiII+8ysiok2ewRyKmqtuln6SAHBZ/Gf5PjV2G1BsIc6udPyL2pyNn0oU0y6SjhuBDOA8ace66bfUc30lcdramxJgr8ZvT2i4csK/+kP9hfoWHZ3/b4yffbf0mjWlftxGrjQi9ZSVFZc2joq33VwVgMSfWuXk6QvJ3WlLNpCruPemxUZXq726erX5TPwMXeqqgk/lHYrGGr74Tn Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/5/26 18:27, Nico Pache wrote: > On Thu, Jul 30, 2026 at 2:34 AM David Hildenbrand (Arm) > wrote: >> >> On 7/29/26 18:54, Nico Pache wrote: >>> On Tue, Jul 21, 2026 at 8:02 AM David Hildenbrand (Arm) >>> wrote: >>> >>> Yes but now all VM_MERGEABLEs lose the underutilized shrinker >>> independent from weather KSM was the one who triggered it. >> >> Because KSM takes care of it? > > KSM only takes care of it in the case of 'use_zero_pages' being set. > If we stop KSM splits from reclaiming, we regain the intended sysctl > behavior; otherwise, KSM splits and reclaims indiscriminately. The > secondary effect is that if we don't have this toggle set, the split > would still reclaim these pages. KSM then has to process those pages > (despite them already being freed), wasting cycles. > > Your proposed solution works too, I just think its a more aggressive > approach (stop all VM_MERGEABLEs from split-reclaiming, not just those > that are currently being operated on by KSM). I think we should really just stop two mechanisms to compete entirely: if A is active for a region, B is disabled. Not trying to follow "who split what" and operate based on that. -- Cheers, David