linux-kernel - Re: Background memory scrubbing

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Date:	Mon, 25 Apr 2011 10:53:46 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Robert Whitton <rwhitton@....org>,
	Clemens Ladisch <clemens@...isch.de>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Background memory scrubbing

On 04/20/2011 10:01 AM, Borislav Petkov wrote:
> 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 :).

There was a thread back in 2009 cwith the subject "marching through all
physical memory in software" that discussed some of the issues of a
software background scrub.

Chris

-- 
Chris Friesen
Software Developer
GENBAND
chris.friesen@...band.com
www.genband.com
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