From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id 90AAE6B0035 for ; Tue, 5 Nov 2013 01:32:40 -0500 (EST) Received: by mail-pa0-f47.google.com with SMTP id lf10so8129949pab.34 for ; Mon, 04 Nov 2013 22:32:40 -0800 (PST) Received: from psmtp.com ([74.125.245.116]) by mx.google.com with SMTP id yj4si12831694pac.282.2013.11.04.22.32.39 for ; Mon, 04 Nov 2013 22:32:39 -0800 (PST) Received: by mail-oa0-f47.google.com with SMTP id k1so141207oag.6 for ; Mon, 04 Nov 2013 22:32:37 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <160824051.3072.1382685914055.JavaMail.mail@webmail07> Date: Mon, 4 Nov 2013 22:32:37 -0800 Message-ID: Subject: Re: Disabling in-memory write cache for x86-64 in Linux II From: "Figo.zhang" Content-Type: multipart/alternative; boundary=001a11c25700dc144704ea68326d Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: "Artem S. Tashkinov" , Wu Fengguang , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , Jens Axboe , linux-mm --001a11c25700dc144704ea68326d Content-Type: text/plain; charset=ISO-8859-1 > Yeah, I think we default to a 10% "dirty background memory" (and > allows up to 20% dirty), so on your 16GB machine, we allow up to 1.6GB > of dirty memory for writeout before we even start writing, and twice > that before we start *waiting* for it. > > On 32-bit x86, we only count the memory in the low 1GB (really > actually up to about 890MB), so "10% dirty" really means just about > 90MB of buffering (and a "hard limit" of ~180MB of dirty). > => On 32-bit system, the page cache also can use the high memory, so the size of 10% "dirty background memory" maybe 1.6GB for this case. > > --001a11c25700dc144704ea68326d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable




Yeah, I think we default to a 10% "dirty background memory"= (and
allows up to 20% dirty), so on your 16GB machine, we allow up to 1.6GB
of dirty memory for writeout before we even start writing, and twice
that before we start *waiting* for it.

On 32-bit x86, we only count the memory in the low 1GB (really
actually up to about 890MB), so "10% dirty" really means just abo= ut
90MB of buffering (and a "hard limit" of ~180MB of dirty).
=3D> On 32-bit system, the page cache also can use the hi= gh memory, so =A0the size of 10% "dirty background memory" maybe = 1.6GB for this case.

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