Messages in this thread | | | Date | Wed, 26 Dec 2007 02:17:56 -0800 | From | Arjan van de Ven <> | Subject | Re: Testing RAM from userspace / question about memmap= arguments |
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On Wed, 26 Dec 2007 00:09:57 +0100 Pavel Machek <pavel@ucw.cz> wrote:
> On Sat 2007-12-22 12:09:59, Arjan van de Ven wrote: > > On Tue, 18 Dec 2007 17:06:24 +0000
> > 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...
that's... not nearly usable or enough. Caches are relatively smart about things like use-once.... and they're huge. 12Mb today. You'd need patterns bigger than 100Mb to get even close to being reasonably confident that there's nothing left.
> ... 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.
and a new syscall of some sorts I suspect; "flush all caches" is a ring 0 operation (and you probably need to do it in an ipi anyway on all cpus)
-- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org
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