From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id DAEF85F0001 for ; Sat, 31 Jan 2009 16:28:12 -0500 (EST) Date: Sat, 31 Jan 2009 22:27:55 +0100 From: Pavel Machek Subject: Re: marching through all physical memory in software Message-ID: <20090131212754.GA15243@elf.ucw.cz> References: <715599.77204.qm@web50111.mail.re2.yahoo.com> <49836114.1090209@buttersideup.com> <4984489C.8020309@buttersideup.com> <20090131134327.GB28763@khazad-dum.debian.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090131134327.GB28763@khazad-dum.debian.net> Sender: owner-linux-mm@kvack.org To: Henrique de Moraes Holschuh Cc: Tim Small , "Eric W. Biederman" , ncunningham-lkml@crca.org.au, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Friesen , Doug Thompson , bluesmoke-devel@lists.sourceforge.net, Arjan van de Ven List-ID: Hi! > And if an uncorretable error is detected during the scrub, we have to > do something about it as well. And that won't be that easy: locate > whatever process is using that page, and so something smart to it... > or do some emergency evasive actions if it is one of the kernel's data > scructures, etc. > > So, as you said, "background scrubbing" and "software scrubbing" really are > very different things, and one has to expect that background scrubbing will > eventually trigger software scrubbing, major system emergency handling > (uncorrectable errors in kernel memory) or minor system emergency > handling (uncorrectable errors in process memory). > > > There is (AFAIK) no need to do any writes here, and in fact doing so is > > One might want the possibility of doing inconditional writes, because > it helps with memory bitrot on crappy hardware where the refresh > cycles aren't enough to avoid bitrot. But you definately won't want > it most of the time. > > You can also implement software-based ECC using a background scrubber > and setting aside pages to store the ECC information. Now, THAT is > probably not worth bothering with due to the performance impact, but > who knows... Actually, that would be quite cool. a) I suspect memory in my zaurus bitrots and b) bitroting memory over s2ram is apprently quite common. 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