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[68.160.141.91]) by smtp.gmail.com with ESMTPSA id s17-20020ad44b31000000b0068c523609e6sm777249qvw.20.2024.01.29.09.42.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jan 2024 09:42:39 -0800 (PST) Date: Mon, 29 Jan 2024 12:42:38 -0500 From: Mike Snitzer To: Ming Lei , Dave Chinner , Matthew Wilcox Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Don Dutile , Raghavendra K T , Alexander Viro , Christian Brauner , linux-block@vger.kernel.org Subject: Re: [RFC PATCH] mm/readahead: readahead aggressively if read drops in willneed range Message-ID: References: <20240128142522.1524741-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 0EF48180004 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: jadsdanbjz5ijyxy8cr5sn17id1nep3k X-HE-Tag: 1706550160-141802 X-HE-Meta: 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 St55R7JL 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 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 Mon, Jan 29 2024 at 12:19P -0500, Mike Snitzer wrote: > While I'm sure this legacy application would love to not have to > change its code at all, I think we can all agree that we need to just > focus on how best to advise applications that have mixed workloads > accomplish efficient mmap+read of both sequential and random. > > To that end, I heard Dave clearly suggest 2 things: > > 1) update MADV/FADV_SEQUENTIAL to set file->f_ra.ra_pages to > bdi->io_pages, not bdi->ra_pages * 2 > > 2) Have the application first issue MADV_SEQUENTIAL to convey that for > the following MADV_WILLNEED is for sequential file load (so it is > desirable to use larger ra_pages) > > This overrides the default of bdi->io_pages and _should_ provide the > required per-file duality of control for readahead, correct? I meant "This overrides the default of bdi->ra_pages ..." ;)