From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f170.google.com (mail-pd0-f170.google.com [209.85.192.170]) by kanga.kvack.org (Postfix) with ESMTP id 75CC56B00C4 for ; Wed, 6 Nov 2013 03:42:44 -0500 (EST) Received: by mail-pd0-f170.google.com with SMTP id v10so9991458pde.1 for ; Wed, 06 Nov 2013 00:42:44 -0800 (PST) Received: from psmtp.com ([74.125.245.123]) by mx.google.com with SMTP id ph6si16336491pbb.97.2013.11.06.00.42.41 for ; Wed, 06 Nov 2013 00:42:42 -0800 (PST) Date: Wed, 6 Nov 2013 03:42:20 -0500 (EST) From: Jerome Marchand Message-ID: <1450211196.19341043.1383727340985.JavaMail.root@redhat.com> In-Reply-To: <20131105155319.732dcbefb162c2ee4716ef9d@linux-foundation.org> References: <1382101019-23563-1-git-send-email-jmarchan@redhat.com> <1382101019-23563-2-git-send-email-jmarchan@redhat.com> <20131105155319.732dcbefb162c2ee4716ef9d@linux-foundation.org> Subject: Re: [PATCH v4 2/2] mm: allow to set overcommit ratio more precisely MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave hansen ----- Original Message ----- > From: "Andrew Morton" > To: "Jerome Marchand" > Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "dave hansen" > Sent: Wednesday, November 6, 2013 12:53:19 AM > Subject: Re: [PATCH v4 2/2] mm: allow to set overcommit ratio more precisely > > On Fri, 18 Oct 2013 14:56:59 +0200 Jerome Marchand > wrote: > > > Some applications that run on HPC clusters are designed around the > > availability of RAM and the overcommit ratio is fine tuned to get the > > maximum usage of memory without swapping. With growing memory, the 1% > > of all RAM grain provided by overcommit_ratio has become too coarse > > for these workload (on a 2TB machine it represents no less than > > 20GB). > > > > This patch adds the new overcommit_ratio_ppm sysctl variable that > > allow to set overcommit ratio with a part per million precision. > > The old overcommit_ratio variable can still be used to set and read > > the ratio with a 1% precision. That way, overcommit_ratio interface > > isn't broken in any way that I can imagine. > > The way we've permanently squished this mistake in the past is to > switch to "bytes". See /proc/sys/vm/*bytes. > > Would that approach work in this case? > That was my first version of this patch (actually "kbytes" to avoid overflow). Dave raised the issue that it silently breaks the user interface: overcommit_ratio is zero while the system behaves differently. Jerome -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org