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[209.85.208.172]) by smtp.gmail.com with ESMTPSA id r11sm755451ljh.23.2019.09.20.16.10.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Sep 2019 16:10:18 -0700 (PDT) Received: by mail-lj1-f172.google.com with SMTP id e17so8511539ljf.13 for ; Fri, 20 Sep 2019 16:10:18 -0700 (PDT) X-Received: by 2002:a2e:3e07:: with SMTP id l7mr10586601lja.180.1569021018229; Fri, 20 Sep 2019 16:10:18 -0700 (PDT) MIME-Version: 1.0 References: <156896493723.4334.13340481207144634918.stgit@buzz> In-Reply-To: From: Linus Torvalds Date: Fri, 20 Sep 2019 16:10:01 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2] mm: implement write-behind policy for sequential file writes To: Konstantin Khlebnikov Cc: linux-fsdevel , Linux-MM , Linux Kernel Mailing List , Jens Axboe , Michal Hocko , Dave Chinner , Mel Gorman , Johannes Weiner , Tejun Heo Content-Type: text/plain; charset="UTF-8" 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: On Fri, Sep 20, 2019 at 4:05 PM Linus Torvalds wrote: > > > Now, I hear you say "those are so small these days that it doesn't > matter". And maybe you're right. But particularly for slow media, > triggering good streaming write behavior has been a problem in the > past. Which reminds me: the writebehind trigger should likely be tied to the estimate of the bdi write speed. We _do_ have that avg_write_bandwidth thing in the bdi_writeback structure, it sounds like a potentially good idea to try to use that to estimate when to do writebehind. No? Linus