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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4e8aaf34313sm75504191cf.6.2025.10.21.09.05.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Oct 2025 09:06:00 -0700 (PDT) Date: Tue, 21 Oct 2025 12:05:58 -0400 From: Gregory Price To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com Subject: Re: [RFC PATCH v2] page_alloc: allow migration of smaller hugepages during contig_alloc. Message-ID: References: <20251020210816.1089910-1-gourry@gourry.net> <10402943-b613-4bd6-ab78-f34efa74a95c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10402943-b613-4bd6-ab78-f34efa74a95c@redhat.com> X-Stat-Signature: om1n9spaji9zf6wsotgfguesibe4ug6s X-Rspamd-Queue-Id: B68E51C0018 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761062761-666619 X-HE-Meta: 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 g8mc8YDu I8RRxZ+632A8EEV90MloqiQtL6Zhyjv93maS5wfs93brcD+ELJfiA5vMg3dliZXEBVBs6JWdxxPcKV2HK59Hse6qquGDxl52slh7MzlTZPfOPSWQ7tWxY6+SZVN3uyY47qceInf+IGnE/AFKr0hj9CXEO3AYhga67eV9qWu6Z9zbuaCgdcOmQ2gtV7UN44knfM7ckQ8H7DF1MM/XF6C+VVq4X4v1il8G97WEXgfjlRJij/55l8k6MxASJ6jvY8Y0s5Xoa+ZCaJefq9+sySYs0z0RmvztzqYqMiYS3DVe3tqqbK3AYiIOZSQCMSrKjPGJyo1JAWJzllTvYfVskrvsz4Td1AsiJpq5Y4Hm5TNEVNZm3hzBc/6T/USH5PQ== 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, Oct 21, 2025 at 11:30:48AM +0200, David Hildenbrand wrote: > > Compaction `isolate_migrate_pages_block()` already expects requests > > Please, let's not talk about "compaction" here, it's just confusing to talk > about compaction for something that is not compaction but uses some > primitives (because not properly separated yet) > > Just say "isolate_migrate_pages_block() already expects ..." > will do > > + /* Don't consider moving same size/larger pages */ > > + page = compound_head(page); > > + order = compound_order(page); > > + if ((order >= MAX_PAGE_ORDER) || > > + (nr_pages < (1 << order))) > > + return false; > > This is roughly what we do in pageblock_skip_persistent(), just with a > hardcoded pageblock size. > > I'm not sure about the MAX_PAGE_ORDER check, though. If an arch supports two > hugetlb sizes that exceed MAX_PAGE_ORDER, it would not work as expected. > > Doesn't arm64 support that with cont-PMD vs. PUD hugetlb folios? > MAX_FOLIO_ORDER would be better. Will adjust to MAX_FOLIO_ORDER, makes sense. Missed that. Will take a look at the pageblock code, I think I was looking at the compaction and some other code for inspiration here. ~Gregory