linux-kernel - Re: marching through all physical memory in software

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Message-ID: <20090128193813.GD1222@ucw.cz>
Date:	Wed, 28 Jan 2009 20:38:13 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Chris Friesen <cfriesen@...tel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, Doug Thompson <norsk5@...oo.com>,
	linux-mm@...ck.org, bluesmoke-devel@...ts.sourceforge.net
Subject: Re: marching through all physical memory in software

On Tue 2009-01-27 12:16:52, Eric W. Biederman wrote:
> "Chris Friesen" <cfriesen@...tel.com> writes:
> 
> > Arjan van de Ven wrote:
> >> On Mon, 26 Jan 2009 09:38:13 -0600
> >> "Chris Friesen" <cfriesen@...tel.com> wrote:
> >>
> >>> Someone is asking me about the feasability of "scrubbing" system
> >>> memory by accessing each page and handling the ECC faults.
> >>>
> >>
> >> Hi,
> >>
> >> I would suggest that you look at the "edac" subsystem, which tries to
> >> do exactly this....
> 
> 
> > edac appears to currently be able to scrub the specific page where the fault
> > occurred.  This is a useful building block, but doesn't provide the ability to
> > march through all of physical memory.
> 
> Well that is the tricky part.  The rest is simply finding which physical
> addresses are valid.  Either by querying the memory controller or looking
> at the range the BIOS gave us.
> 
> That part should not be too hard.  I think it simply has not been implemented
> yet as most ECC chipsets implement this in hardware today.

You can do the scrubbing today by echo reboot > /sys/power/disk; echo
disk > /sys/power/state :-)... or using uswsusp APIs.

Take a look at hibernation code for 'walk all memory' examples...  

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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