Re: assert/crash in __rmqueue() when enabling CONFIG_NUMA

[Nick Piggin]

Dave Hansen wrote:

> Ahhh.  I hadn't made the ia64 connection.  I wonder if it is worth
> making CONFIG_HOLES_IN_ZONE say ia64 or something about vmem_map in it
> somewhere.  Might be worth at least a comment like this:
>
> +               if (page_in_zone_hole(buddy)) /* noop on all but ia64 */
> +                       break;
> +               else if (page_zonenum(buddy) != page_zonenum(page))
> +                       break;
> +               else if (!page_is_buddy(buddy, order))
>                         break;          /* Move the buddy up one level. */
>
> BTW, wasn't the whole idea of discontig to have holes in zones (before
> NUMA) without tricks like this? ;)

Yes.

I don't like the patch much, because all that logic should be moved
into page_is_buddy where I put it (surely it is more readable not to
have the checks spilling out -- a page which is not in the correct
zone or is a "hole" is by definition not a buddy, right?)

So, I agree with adding the zone check if any architecture needs it.
But it would be something under CONFIG_HOLES_IN_ZONE, and the arch
needs to *either* align zones correctly (as they've always had to),
or turn this option on.

Thanks for working at this, everyone.

--
SUSE Labs, Novell Inc.
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