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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id t13sm4039319otp.42.2021.03.01.12.16.30 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Mon, 01 Mar 2021 12:16:31 -0800 (PST) Date: Mon, 1 Mar 2021 12:16:19 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Yu Zhao cc: "Kirill A. Shutemov" , Matthew Wilcox , akpm@linux-foundation.org, alex.shi@linux.alibaba.com, vbabka@suse.cz, guro@fb.com, hannes@cmpxchg.org, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, vdavydov.dev@gmail.com Subject: Re: [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and PG_unevictable In-Reply-To: Message-ID: References: <20210224084807.2179942-1-yuzhao@google.com> <20210226091718.2927291-1-yuzhao@google.com> <20210226091718.2927291-4-yuzhao@google.com> <20210226121314.GB2723601@casper.infradead.org> <20210301115007.mgw5vthgjoibnjf4@box> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 1 Mar 2021, Yu Zhao wrote: > On Mon, Mar 01, 2021 at 02:50:07PM +0300, Kirill A. Shutemov wrote: > > On Fri, Feb 26, 2021 at 12:13:14PM +0000, Matthew Wilcox wrote: > > > On Fri, Feb 26, 2021 at 02:17:18AM -0700, Yu Zhao wrote: > > > > All places but one test, set or clear PG_active and PG_unevictable on > > > > small or head pages. Use compound_head() explicitly for that singleton > > > > so the rest can rid of redundant compound_head(). > > > > > > How do you know it's only one place? I really wish you'd work with me > > > on folios. They make the compiler prove that it's not a tail page. > > > > +1 to this. > > > > The problem with compound_head() is systemic and ad-hoc solution to few > > page flags will only complicate the picture. > > Well, I call it an incremental improvement, and how exactly does it > complicate the picture? > > I see your point: you prefer a complete replacement. But my point is > not about the preference; it's about presenting an option: I'm not > saying we have to go with this series; I'm saying if you don't want > to wait, here is something quick but not perfect. +1 to this. Hugh