Re: [PATCH 5/6] Have ia64 use add_active_range() and free_area_init_nodes

On Mon, 15 May 2006 11:19:27 +0100
Andy Whitcroft [off-list ref] wrote:

Nick Piggin wrote:

quoted

Andy Whitcroft wrote:

quoted

Interesting.  You are correct there was no config component, at the time
I didn't have direct evidence that any architecture needed it, only that
we had an unchecked requirement on zones, a requirement that had only
recently arrived with the changes to free buddy detection.  I note that

Recently arrived? Over a year ago with the no-buddy-bitmap patches,
right? Just checking because I that's what I'm assuming broke it...

Yep, sorry I forget I was out of the game for 6 months!  And yes that
was when the requirements were altered.

When no-bitmap-buddy patches was included,

1. bad_range() is not covered by CONFIG_VM_DEBUG. It always worked.
==
static int bad_range(struct zone *zone, struct page *page)
{
        if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
                return 1;
        if (page_to_pfn(page) < zone->zone_start_pfn)
                return 1;
==
And , this code
==
                buddy = __page_find_buddy(page, page_idx, order);

                if (bad_range(zone, buddy))
                        break;
==

checked whether buddy is in zone and guarantees it to have page struct.


But clean-up/speed-up codes vanished these checks. (I don't know when this occurs)
Sorry for misses these things.

-Kame