[sf-lug] memory integrity checking / excluding bad memory
asheesh at asheesh.org
Sat Feb 2 16:25:20 PST 2008
On Sat, 2 Feb 2008, Kristian Erik Hermansen wrote:
> On Feb 2, 2008 2:54 PM, Alex Kleider <a_kleider at yahoo.com> wrote:
>> Also, please, what's the command to exclude the memory that is
>> discovered to be bad?
> Sameer already told you the other answer, but here's this one. There
> is a neat trick that Asheesh came up with, that I didn't know of, that
> allows you to restrict the running kernel memory mapping to a selected
> allocated chunk. Basically, we passed the kernel the mem=512M option
> so that we could exclude the dim module that we thought was bad, and
> thus prevent it form being utilized in the OS during installation.
> However, we are not sure how that option is implemented. Does it grab
> the first 512 megs of RAM, distribute it across both sticks, just grab
> randomly from a chunk pool?
It should do the lower 512 physical megabytes of RAM.
> We didn't investigate. However, it
> didn't work (perhaps the first DIMM was bad?), but I;m sure if anyone
> has info on how that is implemented we would love to hear about it :-)
> Not gonna go dig the sources myself right now...heh
Another more reasonable option is to use the badmem patch -
http://badmem.sourceforge.net/ - that lets you specify exactly which parts
of RAM are bad. (You can get this list from memtest86.)
But in general, such hacks are frowned-upon - if you have bad hardware,
who knows if more of it will fail in the next ten minutes?
But if it works for you well enough, then so be it....
Just because your doctor has a name for your condition doesn't mean he
knows what it is.
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