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Wed, 28 May 2025 05:25:19 -0700 (PDT) Received: from ed.ac.uk ([2001:630:3c1:90:97e6:f326:b9e:1a85]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4eac8f128sm1368680f8f.60.2025.05.28.05.25.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 May 2025 05:25:19 -0700 (PDT) Date: Wed, 28 May 2025 13:25:13 +0100 From: Karim Manaouil To: Zi Yan Cc: David Hildenbrand , Bharata B Rao , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jonathan.Cameron@huawei.com, dave.hansen@intel.com, gourry@gourry.net, hannes@cmpxchg.org, mgorman@techsingularity.net, mingo@redhat.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, sj@kernel.org, weixugc@google.com, willy@infradead.org, ying.huang@linux.alibaba.com, dave@stgolabs.net, nifan.cxl@gmail.com, joshua.hahnjy@gmail.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, akpm@linux-foundation.org Subject: Re: [RFC PATCH v0 2/2] mm: sched: Batch-migrate misplaced pages Message-ID: <20250528122513.4rxzkia7lge7du5p@ed.ac.uk> References: <20250521080238.209678-1-bharata@amd.com> <20250521080238.209678-3-bharata@amd.com> <62cef618-123c-4ffa-b45a-c38b65d2a5a3@redhat.com> <5d6b92d8-251f-463b-adde-724ea25b2d89@redhat.com> <996B013E-4143-4182-959F-356241BE609A@nvidia.com> <382839fc-ea63-421a-8397-72cb35dd8052@redhat.com> <94BF4806-ABCD-4D01-8577-9E138A634815@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <94BF4806-ABCD-4D01-8577-9E138A634815@nvidia.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A014818000A X-Stat-Signature: 3w41o6z7qzj63nfoo5od4dbyr53en6wi X-Rspam-User: X-HE-Tag: 1748435121-68223 X-HE-Meta: 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 j+fQ4pdA 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 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: On Mon, May 26, 2025 at 10:20:39AM -0400, Zi Yan wrote: > On 26 May 2025, at 5:29, David Hildenbrand wrote: > > PFN scanning can be faster than walking lists, but I suspect it depends on how many pages there really are to be migrated ... and some other factors :) > > Yes. LRU list is good since it restricts the scanning range, but PFN scanning > itself does not have it. PFN scanning with some filter mechanism might work > and that filter mechanism is a way of marking to-be-migrated pages. Of course, > a quick re-evaluation of the to-be-migrated pages right before a migration > would avoid unnecessary work like we discussed above. PFN scanning could be faster because of prefetching, but it pollutes the caches, which may not be nice to the application running on that cpu core before we transitioned to kernel space. -- ~karim