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Thu, 04 Apr 2024 07:21:25 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFhRpq+S4LQZCpwLVYW+GY9j4DweRYw1JwLI2Ay6RMPXkR0iYHpJNomz2Qmf2zJxRBaHVxPfw== X-Received: by 2002:ac8:5c8a:0:b0:431:810c:a96e with SMTP id r10-20020ac85c8a000000b00431810ca96emr2500097qta.1.1712240484909; Thu, 04 Apr 2024 07:21:24 -0700 (PDT) Received: from x1n ([99.254.121.117]) by smtp.gmail.com with ESMTPSA id fk15-20020a05622a558f00b0043439982526sm2514858qtb.22.2024.04.04.07.21.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Apr 2024 07:21:24 -0700 (PDT) Date: Thu, 4 Apr 2024 10:21:21 -0400 From: Peter Xu To: Matthew Wilcox , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huacai Chen , David Hildenbrand , Jason Gunthorpe , Nathan Chancellor , Andrew Morton , WANG Xuerui , Ryan Roberts , loongarch@lists.linux.dev Subject: Re: [PATCH 1/3] mm: Allow anon exclusive check over hugetlb tail pages Message-ID: References: <20240403013249.1418299-1-peterx@redhat.com> <20240403013249.1418299-2-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Stat-Signature: 3jj7ipq8fi98zdrddzijkq6oohfjdkyx X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BE2A8C0032 X-HE-Tag: 1712240489-644357 X-HE-Meta: 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 nRKcftQa DmbU9lGyrzniQDTq5ml6wxbQn2/pT+BQ72kp4rLOkVOllDhGSYzQS8ZQH3Xfp9bT6xo2uBUxU4XexghZ4ZAO971ayB5sxgUnN/swcNSeSZ5Btd3JxdhVCP6Rx3GT9G4Pk2Prlurgm2YwQtpzvzp2+0XS0yA== 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 Thu, Apr 04, 2024 at 03:06:25PM +0100, Matthew Wilcox wrote: > On Thu, Apr 04, 2024 at 09:45:58AM -0400, Peter Xu wrote: > > On Thu, Apr 04, 2024 at 01:05:57AM +0100, Matthew Wilcox wrote: > > > if (PageHuge(page)) > > > page = compound_head(page); > > > > I would think PageHead() check would help us to avoid compound_head() on > > heads, which should still be the majority cases iiuc (assuming page->flags > > is already around in the cache anyway). I've no strong opinion though, as > > I can hardly tell a difference in reality. > > compound_head() includes a check for PageHead(). Adding the check just > makes things slower. They check different fields (compound_head, offset 0x8 for the former). Again I'm ok with either way to go and I don't expect measurable difference.. so if you prefer this I'm happy with it too. Andrew, could you help update with Matthew's fixup? The comment is definitely better than what I wrote in all cases. Thanks, -- Peter Xu