Messages in this thread | | | Date | Tue, 20 May 2008 16:02:42 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: Possible partial miss in pages needed for zone's memory map? |
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On Mon, 19 May 2008 23:19:37 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> On Sat, 17 May 2008 14:19:15 +0200 Johannes Weiner <hannes@saeurebad.de> wrote: > > > Hi, > > > > I stumbled over the following in the zone initialization code. Please > > let me know if I overlooked something here. > > > > hm, no takers. Let's add linux-mm. > > > > > From: Johannes Weiner <hannes@saeurebad.de> > > Subject: [PATCH] Don't drop a partial page in a zone's memory map size > > > > In a zone's present pages number, account for all pages occupied by the > > memory map, including a partial. > > > > Signed-off-by: Johannes Weiner <hannes@saeurebad.de> > > --- > > > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -3378,7 +3378,8 @@ static void __paginginit free_area_init_ > > * is used by this zone for memmap. This affects the watermark > > * and per-cpu initialisations > > */ > > - memmap_pages = (size * sizeof(struct page)) >> PAGE_SHIFT; > > + memmap_pages = > > + PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT; > > if (realsize >= memmap_pages) { > > realsize -= memmap_pages; > > printk(KERN_DEBUG > > I looked in there for 30 seconds and collapsed in confusion over which > variables are in which units. > Hmm, size * sizeof(struct page) is multiple of PAGE_SIZE in many case. Becasue "size" is always alinged to (1 << MAX_ORDER -1) (I believe...).
ex.) In x86 case, (1 << (MAX_ORDER(11) - 1)) * 4 (sizeof(long)) = (1 << 12) = PAGE_SIZE.
But not sure on other archs with various params. I think above fix is correct.
Thanks, -Kame
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