On Tue, 30 Mar 2010, Andrea Arcangeli wrote:
> > Looks like SLUB also uses _mapcount for some fun purposes:
> >
> > struct page {
> > unsigned long flags; /* Atomic flags, some possibly
> > * updated asynchronously */
> > atomic_t _count; /* Usage count, see below. */
> > union {
> > atomic_t _mapcount; /* Count of ptes mapped in mms,
> > * to show when page is mapped
> > * & limit reverse map searches.
> > */
> > struct { /* SLUB */
> > u16 inuse;
> > u16 objects;
> > };
> > };
> >
> > I guess those don't *really* become a problem in practice until we get a
> > really large page size that can hold >=64k objects. But, at that point,
> > we're overflowing the types anyway (or really close to it).
>
> Maybe we should add a BUG_ON in slub in case anybody runs this on
> PAGE_SIZE == 2M (to avoid silent corruption).
SLUB has been verified a long time ago to run fine with 2M pages.
Just specify
slub_min_order=9
on the kernel command line to get a system booted up with 2M slab pages.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>