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b=mImSMcB2fj8+U6igdHjHwBBl9n6p2G8YeAvkcMd6Pi7W55xVTmr1kVs1KZ4SZOC7V m656V0k8TNM6NSoKosDQYfwoMCsy8/zKoWIj2yGCG9jifiFEs8y+7MzV9R2Gwcccy9 FKQa+PH4AzUoVmdlgYOqtxIHCmSJPgbv9Bgr7bHU= Date: Fri, 28 Mar 2025 16:37:00 -0700 From: Andrew Morton To: David Hildenbrand Cc: Jinjiang Tu , osalvador@suse.de, nao.horiguchi@gmail.com, zi.yan@cs.rutgers.edu, linux-mm@kvack.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com Subject: Re: [PATCH] mm/memory_hotplug: fix call folio_test_large with tail page in do_migrate_range Message-Id: <20250328163700.82c9b426bf199102f3d90dcd@linux-foundation.org> In-Reply-To: References: <20250324131750.1551884-1-tujinjiang@huawei.com> <899807c3-931f-43e6-bf3e-188787a4205a@redhat.com> <68ab727b-dc3d-327f-33b6-25bbfce8530e@huawei.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D6181C0003 X-Stat-Signature: yanegramkr79tuo13gtk74fzzqaocygr X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1743205022-408148 X-HE-Meta: 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 63u0U+wp EaxkAIXw4s2MnAHsPIcQkZGM7sfXBM1T0tyH2aZ+QIZ3whAJauV9I6v4pK0yB5oI+WnMhn7cDB4nkScRmP4MY+KmUSsET9qa/8fV7VhjVl2mj/Gh8F44ydOR80JH20GbAah6Joo9X90rNvo6yY6prxM0ErWqqDXYTgSDlptn42JoBByeE11RrayLQgHYHHbImWI2gfSvypVzCy9IirNigi+Mxj0IpFJdLmjEboGGfgH2j52lwZJBzzeqvFY+cBM3J+30H0VTABJc+ajVyU/T4nd0uL/Yp2TLP1e3Rsvu6e3jBuTuhdNftNjZ0N28aNXenCci+/gDSQz4FkmzdWgakQNku2mMkDypkxDwcYOGOHL+bIpZO09hRJwABAX4RZ5OnMWphcH9I29trwDM= 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 Tue, 25 Mar 2025 20:05:50 +0100 David Hildenbrand wrote: > On 25.03.25 04:02, Jinjiang Tu wrote: > > > >> Moving that will not make it able to skip the large frozen > >> (refcount==0, e.g., free hugetlb) folio in the continue/put_folio case > >> above. Hmmmm .. > > For free hugetlb, pfn is increased by 1 in each loop. This leads to skip > > free hugetlb slower. > > Yes. But now I realize that we have the same issue with free buddy pages > already (folio_try_get of each individual page :( ). > > >> > >> We could similarly to dumping folios, snapshot them, so we can read > >> stable data. > > extract the code in __dump_page()? But snapshot may lead to > > do_migrate_range() slower too. > > There is a patch series on the list to do that, but it might take a > while to clean that up. Ideally, we'd also jump over free buddy pages. > In the future we might have better ways to do that. > > I don't consider this change here really important, but if all it > affects is free hugetlb folios, it's not really worth it to have this > code around. > > Acked-by: David Hildenbrand > > But: I suspect 8135d8926c08 is not the introducing commit. Please re-verify. > > We should not CC stable. Why shouldn't we cc:stable? A userspace-triggerable BUG?