Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261392AbUJ0DqN (ORCPT ); Tue, 26 Oct 2004 23:46:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261407AbUJ0DqN (ORCPT ); Tue, 26 Oct 2004 23:46:13 -0400 Received: from fw.osdl.org ([65.172.181.6]:25049 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261392AbUJ0DqF (ORCPT ); Tue, 26 Oct 2004 23:46:05 -0400 Date: Tue, 26 Oct 2004 20:43:08 -0700 From: Andrew Morton To: Nick Piggin Cc: andrea@novell.com, riel@redhat.com, linux-kernel@vger.kernel.org Subject: Re: lowmem_reserve (replaces protection) Message-Id: <20041026204308.73ee438b.akpm@osdl.org> In-Reply-To: <417F1746.2080607@yahoo.com.au> References: <417DCFDD.50606@yahoo.com.au> <20041027005425.GO14325@dualathlon.random> <417F025F.5080001@yahoo.com.au> <20041027022920.GS14325@dualathlon.random> <417F0FA2.4090800@yahoo.com.au> <20041027032338.GU14325@dualathlon.random> <417F1746.2080607@yahoo.com.au> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1022 Lines: 21 Nick Piggin wrote: > > It actually can overscan lower zones a little bit, because > whenever any higher zone in the pgdat is low on memory, then > it and all zones below it get scanned too. Because we know that all of the eligible zones are below pages_low. kswapd will then work to bring all the relevant zones back to pages_high. When working on this code it is very very easy to break the zone levelling: you *have* to run a workload mix and monitor the numbers in /proc/vmstat to ensure that all zones are undergoing page scanning at frequencies which are proportional to their sizes. It's easy to screw up the zone levelling so all allocations end up coming from ZONE_NORMAL and pagecache pages in, say, ZONE_DMA end up just sitting there. - 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/