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SubjectRe: [PATCH 0/2] ia64: Migrate data off physical pages with correctable errors
On Mon, Apr 28, 2008 at 01:33:23PM -0600, Matthew Wilcox wrote:
> On Mon, Apr 28, 2008 at 02:22:52PM -0500, Russ Anderson wrote:
> > There is always an issue of how agressive the code should be on
> > migrating pages. Should it migrate on the first correctable error,
> > or wait for some threshold? Reasonable people may disagree on the
> > threshold and the "right" answer may be hardware specific. The
> > decision making is confined to the cpe_migrate.c code. It is
> > currently set to migrate on the first correctable error.
>
> I think the kernel code should do the migration ASAP. But I think we
> should have a list of 'bad' pages. We could then have a badram driver
> that userspace can talk to to find out which pages are bad, map those
> pages into a badram process, do various tests on them, and return the
> pages to the pool if they're determined to be 'good'.

Sure. The bad page list is badpagelist (defined in mca.c).

> I could also see badramd having a list of pages found to be bad
> in previous boots and asking the badram driver to take them out of
> circulation early in boot before they've been allocated.

That would be one alternative. That type functionality would be
useful. FWIW, some of my testing was on a system with a DIMM with
solid single bits. It is a row/column problem so several meg of
addresses are effected. Each boot it would migrate several meg worth
of pages without any problem. It works surprisingly good.

--
Russ Anderson, OS RAS/Partitioning Project Lead
SGI - Silicon Graphics Inc rja@sgi.com


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