On 7/15/20 1:11 PM, Chris Murphy wrote:
Hi,
While bad RAM is uncommon, it comes up with some regularity to cause
folks a lot of grief. I'm wondering if there's a way to make it easier
to get bad news :-\ In particular there are cases where RAM defects
just don't show up with a few hours of memtest86+, it can take days of
contiguous testing, which is so inconvenient the test itself seems
worse.
Here's what I've got so far:
1. Fedora includes /boot/memtest86+-5.01 on every installation. But this is a
legacy/BIOS program. [..]
2. The kernel has a built-in memory tester. [..]
3. "memory interface test" used at Google,[..]
4. "multiple concurrent kernel compiles"
There's also 5. memtester, http://pyropus.ca/software/memtester/ ,
packaged in Fedora. It runs in userland, so obvously isn't as thorough
but I'd think it has got to better than gcc and other userland
utilities, because it tries the 'known-tricky' access patterns rather
than hoping to see them in compiler output.
I remember the beginnings of memtest86+: its predecessor was written at
the SGI hardware division by folks who understood how e.g specific
access paterns appear on the physical traces on the memory modules, and
can lead to crosstalk, but only if you simulataneously and repeatedly
toggle very specific bits. This type of knowledge was essential to
writing good tests, and probably also to discovering vulnerabilites like
rowhammer.
Have you looked at memtester? What do you think of it?
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