lkml.org 
[lkml]   [2006]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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/

\
 
 \ /
  Last update: 2006-05-15 12:50    [W:0.068 / U:0.616 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site