Messages in this thread | | | Date | Wed, 26 Dec 2007 00:09:57 +0100 | From | Pavel Machek <> | Subject | Re: Testing RAM from userspace / question about memmap= arguments |
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On Sat 2007-12-22 12:09:59, Arjan van de Ven wrote: > On Tue, 18 Dec 2007 17:06:24 +0000 > Matthew Bloch <matthew@bytemark.co.uk> wrote: > > > Hi - I'm trying to come up with a way of thoroughly testing every byte > > of RAM from within Linux on amd64 (so that it can be automated better > > than using memtest86+), and came up with an idea which I'm not sure is > > supported or practical. > > > > The obvious problem with testing memory from user space is that you > > can't mlock all of it, so the best you can do is about three quarters, > > and hope that the rest of the memory is okay. > > well... to be honest the more obvious problem will be that you won't be testing the RAM, you'll be testing the CPU's cache.. over and over again. > > memtest86+ does various magic to basically bypass the caches (by disabling them ;-)... > Doing that in a live kernel situation, and from userspace to boot...... that's... and issue.
Are you sure? I always assumed that memtest just used patterns bigger than L1/L2 caches... ... and IIRC my celeron testing confirmed it, if I disabled L2 cache in BIOS, memtest behave differently.
Anyway, if you can do iopl(), we may as well let you disable caches, but you are right, that will need a kernel patch. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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