Date: Wed, 20 Apr 2011 18:01:26 +0200
From: Borislav Petkov <bp@amd64.org>
To: Robert Whitton <rwhitton@iee.org>
Cc: Clemens Ladisch <clemens@ladisch.de>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: Background memory scrubbing
Message-ID: <20110420160125.GC2312@gere.osrc.amd.com>
References: <18563.1303314382@jupiter.eclipse.co.uk>
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On Wed, Apr 20, 2011 at 04:46:22PM +0100, Robert Whitton wrote:
> 
> > On Wed, Apr 20, 2011 at 05:19:41PM +0200, Clemens Ladisch wrote:
> > > > Unfortunately in common with a large number of hardware platforms
> > > > background scrubbing isn't supported in the hardware (even though ECC
> > > > error correction is supported) and thus there is no BIOS option to
> > > > enable it.
> > > 
> > > Which hardware platform is this? AFAICT all architectures with ECC
> > > (old AMD64, Family 0Fh, Family 10h) also have scrubbing support.
> > > If your BIOS is too dumb, just try enabling it directly (bits 0-4 of
> > > PCI configuration register 0x58 in function 3 of the CPU's northbridge
> > > device, see the BIOS and Kernel's Developer's Guide for details).
> > 
> > Or even better, if on AMD, you can build the amd64_edac module
> > (CONFIG_EDAC_AMD64) and do
> > 
> > echo  > /sys/devices/system/edac/mc/mc/sdram_scrub_rate
> > 
> > where x is the scrubbing bandwidth in bytes/sec and y is the memory
> > controller on the machine, i.e. node.
>
> Unfortunately that also isn't an option on my platform(s). There surely must be a way for a module to be able to get a mapping for each physical page of memory in the system and to be able to use that mapping to do atomic read/writes to scrub the memory.

For such questions I've added just the right ML to Cc :).

-- 
Regards/Gruss,
Boris.

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