From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id CEA996B0083 for ; Fri, 30 Jan 2009 16:10:38 -0500 (EST) Subject: Re: marching through all physical memory in software From: Nigel Cunningham Reply-To: ncunningham-lkml@crca.org.au In-Reply-To: References: <715599.77204.qm@web50111.mail.re2.yahoo.com> Content-Type: text/plain Date: Sat, 31 Jan 2009 08:10:58 +1100 Message-Id: <1233349858.11332.14.camel@nigel-laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: "Eric W. Biederman" Cc: Doug Thompson , Pavel Machek , Chris Friesen , Arjan van de Ven , linux-kernel@vger.kernel.org, linux-mm@kvack.org, bluesmoke-devel@lists.sourceforge.net List-ID: Hi. On Fri, 2009-01-30 at 11:32 -0800, Eric W. Biederman wrote: > Doug Thompson writes: > > > Nigel Cunningham wrote: > > > > Hi again. > > > > On Fri, 2009-01-30 at 10:13 +0100, Pavel Machek wrote: > > > > Hi. > > > > > > > > On Wed, 2009-01-28 at 20:38 +0100, Pavel Machek wrote: > > > > > You can do the scrubbing today by echo reboot > /sys/power/disk; echo > > > > > disk > /sys/power/state :-)... or using uswsusp APIs. > > > > > > > > That won't work. The RAM retains its contents across a reboot, and even > > > > for a little while after powering off. > > > > > > Yes, and the original goal was to rewrite all the memory with same > > > contents so that parity errors don't accumulate. SO scrubbing here != > > > trying to clear it. > > > > Sorry - I think I missed something. > > > > AFAICS, hibernating is going to be a noop as far as doing anything to > > memory that's not touched by the process of hibernating goes. It won't > > clear it or scrub it or anything else. > > A background software scrubber simply has the job of rewritting memory > to it's current content so that the data and the ecc check bits are > guaranteed to be in sync keeping correctable ecc errors caused by > environmental factors from accumulating. > > Pavel's original comment was that the hibernation code has to walk all > of memory to save it to disk so it would be a good place to look to > figure out how to walk all of memory. And incidentally hibernation > would serve as a crud way of rewritting all of memory. Thanks. Now I get it :) Nigel -- 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