Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755865AbYH1RIX (ORCPT ); Thu, 28 Aug 2008 13:08:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753222AbYH1RIO (ORCPT ); Thu, 28 Aug 2008 13:08:14 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:33510 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751776AbYH1RIN (ORCPT ); Thu, 28 Aug 2008 13:08:13 -0400 Date: Thu, 28 Aug 2008 17:51:00 +0100 From: Alan Cox To: david@lang.hm Cc: linux-kernel Subject: Re: question about overcommit Message-ID: <20080828175100.3c3cda9e@lxorguk.ukuu.org.uk> In-Reply-To: References: X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 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 Content-Length: 988 Lines: 20 O> my belief from watching the discussions is that it will evict things from > ram to make space for the new allocation, and as a result running with > overcommit disabled ends up wasting a noticable amount of ram. As a result No-overcommit is address space accounting alone. It doesn't change actual allocation or management of memory, it simply ensures that there should always be enough space to ensure it can sort itself out without having to OOM something. It's a bit like bank loans - providing I know how much money is available I don't have to do much except for ensure the total loaned is covered. In the overcommit mode we instead run like the US banking system and pray we don't hit a messy OOM (out of money) situation. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/