From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 4205D6B0005 for ; Wed, 30 Jan 2013 07:51:53 -0500 (EST) Date: Wed, 30 Jan 2013 13:51:51 +0100 From: Pavel Machek Subject: Re: [RFC] Reproducible OOM with just a few sleeps Message-ID: <20130130125151.GB19069@amd.pavel.ucw.cz> References: <201301142036.r0EKaYGN005907@como.maths.usyd.edu.au> <50F4A92F.2070204@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50F4A92F.2070204@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: paul.szabo@sydney.edu.au, 695182@bugs.debian.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Hi! > > I understand that more RAM leaves less lowmem. What is unacceptable is > > that PAE crashes or freezes with OOM: it should gracefully handle the > > issue. Noting that (for a machine with 4GB or under) PAE fails where the > > HIGHMEM4G kernel succeeds and survives. > > You have found a delta, but you're not really making apples-to-apples > comparisons. The page tables (a huge consumer of lowmem in your bug > reports) have much more overhead on a PAE kernel. A process with a > single page faulted in with PAE will take at least 4 pagetable pages > (it's 7 in practice for me with sleeps). It's 2 pages minimum (and in > practice with sleeps) on HIGHMEM4G. > > There's probably a bug here. But, it's incredibly unlikely to be seen > in practice on anything resembling a modern system. The 'sleep' issue > is easily worked around by upgrading to a 64-bit kernel, or using Are you saying that HIGHMEM configuration with 4GB ram is not expected to work? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org