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[2003:d8:2f22:2e00:6e71:238a:de9f:e396]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a35ca8caaasm23285583f8f.83.2025.05.22.09.26.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 May 2025 09:26:49 -0700 (PDT) Message-ID: <5d6b92d8-251f-463b-adde-724ea25b2d89@redhat.com> Date: Thu, 22 May 2025 18:26:47 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v0 2/2] mm: sched: Batch-migrate misplaced pages To: Zi Yan Cc: 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 References: <20250521080238.209678-1-bharata@amd.com> <20250521080238.209678-3-bharata@amd.com> <62cef618-123c-4ffa-b45a-c38b65d2a5a3@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 22.05.25 18:24, Zi Yan wrote: > On 22 May 2025, at 12:11, David Hildenbrand wrote: > >> On 21.05.25 10:02, Bharata B Rao wrote: >>> Currently the folios identified as misplaced by the NUMA >>> balancing sub-system are migrated one by one from the NUMA >>> hint fault handler as and when they are identified as >>> misplaced. >>> >>> Instead of such singe folio migrations, batch them and >>> migrate them at once. >>> >>> Identified misplaced folios are isolated and stored in >>> a per-task list. A new task_work is queued from task tick >>> handler to migrate them in batches. Migration is done >>> periodically or if pending number of isolated foios exceeds >>> a threshold. >> >> That means that these pages are effectively unmovable for other purposes (CMA, compaction, long-term pinning, whatever) until that list was drained. >> >> Bad. > > Probably we can mark these pages and when others want to migrate the page, > get_new_page() just looks at the page's target node and get a new page from > the target node. How do you envision that working when CMA needs to migrate this exact page to a different location? It cannot isolate it for migration because ... it's already isolated ... so it will give up. Marking might not be easy I assume ... -- Cheers, David / dhildenb