kernel memory checks on boot vs. boot time

Ivan Voras ivoras at
Wed Mar 23 15:57:49 UTC 2011

On 23/03/2011 12:51, Andriy Gapon wrote:
> on 22/03/2011 21:54 Matthew Jacob said the following:
>> John Baldwin wrote:
>>> Do other platforms bother with these sorts of memory tests?  If not I'd vote
>>> to just drop it.  I think this mattered more when you didn't have things like
>>> SMAP (so you had to guess at where memory ended sometimes).  Also, modern
>>> server class x86 machines generally support ECC RAM which will trigger a
>>> machine check if there is a problem.  I doubt that the early checks are
>>> catching anything even for the non-ECC case.
>>> If nothing else, I would definitely drop this from amd64 (all those systems
>>> have SMAP and machine check support, etc.).
>> Memory checks are definitely still useful. Loading the linux mem tester has
>> helped find lots of problems, even on so-called modern machines. I'd voter for
>> leaving this as an option.
> I think that you talk about a different kind of memory checking/testing.
> What we have in FreeBSD looks a lot like what BIOSes use(d) to do on startup.
> Besides, AFAIR, it doesn't report any results to you.

I'd say that is the main point. At least once I've thought the machine 
hung when it was doing this check for a surprisingly long time. I'd vote 
for *at least* adding a "twirling baton" indicator (every 1 GB or so) 
that something is going on, on all platforms :)

If these tests have any effect at all (how can they fail? has anyone 
seen them fail?) I'd vote to keep them enabled by default, with a 
tunable to optionally disable them, as every little bit helps for 
reliability. If there is no effect at all from the tests, then just 
remove them.

More information about the freebsd-arch mailing list