From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937436AbXHMPlt (ORCPT ); Mon, 13 Aug 2007 11:41:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S945885AbXHMNxn (ORCPT ); Mon, 13 Aug 2007 09:53:43 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:45629 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762424AbXHMNxj (ORCPT ); Mon, 13 Aug 2007 09:53:39 -0400 Subject: Re: min_free_kbytes documentation, /proc/sys/vm docs From: Peter Zijlstra To: Pavel Machek Cc: Andrew Morton , kernel list , andrea@suse.de, npiggin@suse.de In-Reply-To: <20070813134626.GA7305@atrey.karlin.mff.cuni.cz> References: <20070813134626.GA7305@atrey.karlin.mff.cuni.cz> Content-Type: text/plain Date: Mon, 13 Aug 2007 15:53:00 +0200 Message-Id: <1187013180.20108.59.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2007-08-13 at 15:46 +0200, Pavel Machek wrote: > Hi! > > min_free_kbytes documentation says: > > min_free_kbytes: > > This is used to force the Linux VM to keep a minimum number > of kilobytes free. The VM uses this number to compute a pages_min > value for each lowmem zone in the system. Each lowmem zone gets > a number of reserved free pages based proportionally on its size. > > ....which is not too helpful :-(. In particular, should kernel survive > setting this to 0 and still work reliably? IOW is this > performance-only tweak, or does it correctness implications? correctness sort-of, since PF_MEMALLOC usage is currently un-bounded. > I guess it should also say something like "do not set this to more > than half of your physical RAM (or half of lowmem?) or you get an > instant OOM". yeah, lowmem, not sure on the oom part, it should work with quite high limits, although I've never tried it with ridiculous numbers.