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Does Linux have a mechanism to "scrub" memory? e.g. testing the memory and marking areas as dirty if they fail so that the system can continue to operate "safely" even with bad ram chips installed?!

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This is actually a bad idea. Memory cannot be reliably tested in a quick sweep. This is why software like memtest86 uses multiple passes with different bit patters to test memory. Solution:

  1. Test memory with memtest86, preferably long test, leave it running overnight, it will take a long time.

  2. If bad memory is detected, use memmap kernel parameter to force kernel not to use that memory:

   memmap=nn[KMG]$ss[KMG]
            [KNL,ACPI] Mark specific memory as reserved.
            Region of memory to be used, from ss to ss+nn.
            Example: Exclude memory from 0x18690000-0x1869ffff
                     memmap=64K$0x18690000
                     or
                     memmap=0x10000$0x18690000

In addition, you can use ECC memory which will correct 1-bit errors and detect 2-bit errors in your memory automatically (and you'll get log messages from kernel about uncorrectable memory problems if they happen)

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Thanks for the tip on those kernel parameters. Do you think you please can clarify why this is a such a bad idea and why you can't check a chunk of memory using the same methods as memtest86(+)? I am aware that more reliable testing requires more CPU time (and probably bigger chunks of ram in one go as well) but why would this have to be a show stopper? CPU time may not a problem if spread over a long enough period and besides multi cpu is becomming more and more mainstream. – Waxhead Dec 28 '11 at 21:32
Well technically, if done over long enough period of time, this may be possible. But the bottleneck here is not CPU(s), but memory bus, and of course you "poison" your CPU's memory cache. I'd not aware of such kernel module, and the idea looks very fragile to me (orchestrating repeated pattern writing to an arbitrary region of memory on a live system, etc.) – haimg Dec 28 '11 at 21:50
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