Messages in this thread | | | Date | Mon, 15 May 2006 19:47:35 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 5/6] Have ia64 use add_active_range() and free_area_init_nodes |
| |
On Mon, 15 May 2006 19:29:18 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Mon, 15 May 2006 11:19:27 +0100 > Andy Whitcroft <apw@shadowen.org> wrote: > > > Nick Piggin wrote: > > > Andy Whitcroft wrote: > > > > > >> 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. >
One more point When above no-bitmap patches was included, the user of not-aligned zones are only ia64, I think. Because ia64 used virtual mem_map, page_to_pfn(page) on CONFIG_DISCONTIG_MEM doesn't access page struct itself.
#define page_to_pfn(page) (page - vmemmap)
So, it didn't panic. ia64/vmemmap was safe.
If other archs used not-aligned zone + CONFIG_DISCONTIGMEM, not-aligned-zones problem would come out earlier.
-Kame
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |