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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c096a8c758sm193246585a.24.2025.12.19.06.27.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Dec 2025 06:27:17 -0800 (PST) Date: Fri, 19 Dec 2025 09:26:40 -0500 From: Gregory Price To: Wei Yang 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, osalvador@suse.de, rientjes@google.com, david@redhat.com, joshua.hahnjy@gmail.com, fvdl@google.com Subject: Re: [PATCH v6] page_alloc: allow migration of smaller hugepages during contig_alloc Message-ID: References: <20251218233804.1395835-1-gourry@gourry.net> <20251219000800.tnpqzvcdyeqcwryt@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251219000800.tnpqzvcdyeqcwryt@master> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 4AD5E8000F X-Stat-Signature: 9a56ken6k7c87utm9a6m38nfswanwodn X-HE-Tag: 1766154439-463073 X-HE-Meta: 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 INCnb1KH baA1OXzHL5nmW2Yf5T8GIs92n8BjipHks6snjnMRsYPs7UZths5FXMCxA8E7UAfiYJLrsaKCgrPliJ7T2qF0Cgo0RkW+jlaFosZ8+rxCQ5LoTK4GBNAiKwvTQh00sAswstFxkUWCo1Vf4LkDGq4s5XIp4Zgotc7TqxoXPiTmzHfCgVdUimd2ypAmff9d7Km1/JnZqLfSHOd7dfVZrOoIbN492LK4phNIjETpqtfkT9pw/kZr8dXuG10QHdbw3C3VH3t0dvwLezwyiS5dmkeTgsezPwwuu4YMGVCeSxrPQrU7HPTHKxBmY5fCzRCFmwnA+fLZChXJPY5G+ljvompQfE24d8kZY3PPa9dMEHMfJDRUL4Zkae4l/lghAp6ak8E6rmAw8ByUG5dGXAQc0q40qAoz9lNxrgCTQN6XgfugyKuJbICbKVWSOOlV/f7z4GHs65hFT 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 Fri, Dec 19, 2025 at 12:08:00AM +0000, Wei Yang wrote: > >+ > >+ page = compound_head(page); > >+ order = compound_order(page); > > The order is get from head page. > > >+ if ((order >= MAX_FOLIO_ORDER) || > >+ (nr_pages <= (1 << order))) > >+ return false; > >+ > >+ /* No need to check the pfns for this page */ > >+ i += (1 << order) - 1; > > So this advance should based on "head page" instead of original page, right? > hm, I think the thought here was that since we're moving forward from start of an aligned chunk, we'd never hit a non-head page - but this may not be true. Will think about this for a bit. ~Gregory