From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755900Ab3KEXxV (ORCPT ); Tue, 5 Nov 2013 18:53:21 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:59510 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755558Ab3KEXxU (ORCPT ); Tue, 5 Nov 2013 18:53:20 -0500 Date: Tue, 5 Nov 2013 15:53:19 -0800 From: Andrew Morton To: Jerome Marchand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com Subject: Re: [PATCH v4 2/2] mm: allow to set overcommit ratio more precisely Message-Id: <20131105155319.732dcbefb162c2ee4716ef9d@linux-foundation.org> In-Reply-To: <1382101019-23563-2-git-send-email-jmarchan@redhat.com> References: <1382101019-23563-1-git-send-email-jmarchan@redhat.com> <1382101019-23563-2-git-send-email-jmarchan@redhat.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?