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Sun, 21 Mar 2021 19:52:46 -0700 (PDT) Received: from localhost ([58.84.78.96]) by smtp.gmail.com with ESMTPSA id f14sm12396837pfk.92.2021.03.21.19.52.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 Mar 2021 19:52:45 -0700 (PDT) Date: Mon, 22 Mar 2021 12:52:40 +1000 From: Nicholas Piggin Subject: Re: [PATCH v4 01/25] mm: Introduce struct folio To: Balbir Singh , Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210305041901.2396498-1-willy@infradead.org> <20210305041901.2396498-2-willy@infradead.org> <20210318235645.GB3346@balbir-desktop> <20210319012527.GX3420@casper.infradead.org> In-Reply-To: <20210319012527.GX3420@casper.infradead.org> MIME-Version: 1.0 Message-Id: <1616381339.fjexi9aqhl.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A78985001522 X-Stat-Signature: we1n6mymzaax3h53jc5ga6eyrhc4n3he Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=mail-pf1-f178.google.com; client-ip=209.85.210.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616381565-499971 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: Excerpts from Matthew Wilcox's message of March 19, 2021 11:25 am: > On Fri, Mar 19, 2021 at 10:56:45AM +1100, Balbir Singh wrote: >> On Fri, Mar 05, 2021 at 04:18:37AM +0000, Matthew Wilcox (Oracle) wrote: >> > A struct folio refers to an entire (possibly compound) page. A functi= on >> > which takes a struct folio argument declares that it will operate on t= he >> > entire compound page, not just PAGE_SIZE bytes. In return, the caller >> > guarantees that the pointer it is passing does not point to a tail pag= e. >> > >>=20 >> Is this a part of a larger use case or general cleanup/refactor where >> the split between page and folio simplify programming? >=20 > The goal here is to manage memory in larger chunks. Pages are now too > small for just about every workload. Even compiling the kernel sees a 7% > performance improvement just by doing readahead using relatively small > THPs (16k-256k). You can see that work here: > https://git.infradead.org/users/willy/pagecache.git/shortlog/refs/heads/m= aster The 7% improvement comes from cache cold kbuild by improving IO patterns? Just wondering what kind of readahead is enabled by this that can't be done with base page size. Thanks, Nick