Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 2 Nov 2001 15:58:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 2 Nov 2001 15:58:15 -0500 Received: from humbolt.nl.linux.org ([131.211.28.48]:31129 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Fri, 2 Nov 2001 15:57:55 -0500 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Sven Heinicke , linux-kernel@vger.kernel.org Subject: Re: Google's mm problem - not reproduced on 2.4.13 Date: Fri, 2 Nov 2001 21:58:53 +0100 X-Mailer: KMail [version 1.3.2] In-Reply-To: <20011102181758Z16039-4784+420@humbolt.nl.linux.org> <200111022027.fA2KRwe20006@penguin.transmeta.com> In-Reply-To: <200111022027.fA2KRwe20006@penguin.transmeta.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Cc: Ben Smith , Andrea Arcangeli , Rik van Riel Message-Id: <20011102205746Z16039-4784+457@humbolt.nl.linux.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On November 2, 2001 09:27 pm, Linus Torvalds wrote: > In article <20011102181758Z16039-4784+420@humbolt.nl.linux.org>, > Daniel Phillips wrote: > > > >It's hard to see how that could be wrong. Plus, this test program does > >run under 2.4.9, it just uses way too much CPU on that kernel. So I'd say > >mm bug. > > So how much memory is mlocked? I'm not sure exactly, I didn't run the test. I *think* it's just over 50% of physical memory. > The locked memory will stay in the inactive list (it won't even ever be > activated, because we don't bother even scanning the mapped locked > regions), and the inactive list fills up with pages that are completely > worthless. Yes, it does various things on various vms. On 2.4.9 it stays on the inactive list until free memory gets down to rock bottom, then most of it moves to the active list and the system reaches a steady state where it can operate, though with kswapd grabbing 99% CPU (two processor system), but the test does complete. On the current kernel the it dies. > And the kernel will decide that because most of the unfreeable pages are > mapped, it needs to do VM scanning, which obviously doesn't help. > > Why _does_ this thing do mlock, anyway? What's the point? And how much > does it try to lock? It's how the google database engine works, and keeps latency down, by mapping big database files into memory. I didn't get more information than that on the application. > If root wants to shoot himself in the head by mlocking all of memory, > that's not a VM problem, that's a stupid administrator problem. In the tests I did, it was about 1 gig out of 2. I'm not sure how much memory is mlocked in the 3.5 Gig test the one that's failing, but it's certainly not anything like all of memory. Really, we should be able to mlock 90%+ of memory without falling over. -- Daniel - 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/