Messages in this thread |  | | | Date | Wed, 19 Aug 2009 22:19:46 +0900 | | Subject | Re: [RFC] respect the referenced bit of KVM guest pages? | | From | KOSAKI Motohiro <> |
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2009/8/19 Minchan Kim <minchan.kim@gmail.com>: > On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang<fengguang.wu@intel.com> wrote: >> On Wed, Aug 19, 2009 at 08:05:19PM +0800, KOSAKI Motohiro wrote: >>> >> page_referenced_file? >>> >> I think we should change page_referenced(). >>> > >>> > Yeah, good catch. >>> > >>> >> >>> >> Instead, How about this? >>> >> ============================================== >>> >> >>> >> Subject: [PATCH] mm: stop circulating of referenced mlocked pages >>> >> >>> >> Currently, mlock() systemcall doesn't gurantee to mark the page PG_Mlocked >>> > >>> > mark PG_mlocked >>> > >>> >> because some race prevent page grabbing. >>> >> In that case, instead vmscan move the page to unevictable lru. >>> >> >>> >> However, Recently Wu Fengguang pointed out current vmscan logic isn't so >>> >> efficient. >>> >> mlocked page can move circulatly active and inactive list because >>> >> vmscan check the page is referenced _before_ cull mlocked page. >>> >> >>> >> Plus, vmscan should mark PG_Mlocked when cull mlocked page. >>> > >>> > PG_mlocked >>> > >>> >> Otherwise vm stastics show strange number. >>> >> >>> >> This patch does that. >>> > >>> > Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> >>> >>> Thanks. >>> >>> >>> >>> >> Index: b/mm/rmap.c >>> >> =================================================================== >>> >> --- a/mm/rmap.c 2009-08-18 19:48:14.000000000 +0900 >>> >> +++ b/mm/rmap.c 2009-08-18 23:47:34.000000000 +0900 >>> >> @@ -362,7 +362,9 @@ static int page_referenced_one(struct pa >>> >> * unevictable list. >>> >> */ >>> >> if (vma->vm_flags & VM_LOCKED) { >>> >> - *mapcount = 1; /* break early from loop */ >>> >> + *mapcount = 1; /* break early from loop */ >>> >> + *vm_flags |= VM_LOCKED; /* for prevent to move active list */ >>> > >>> >> + try_set_page_mlocked(vma, page); >>> > >>> > That call is not absolutely necessary? >>> >>> Why? I haven't catch your point. >> >> Because we'll eventually hit another try_set_page_mlocked() when >> trying to unmap the page. Ie. duplicated with another call you added >> in this patch.
Correct.
> Yes. we don't have to call it and we can make patch simple. > I already sent patch on yesterday. > > http://marc.info/?l=linux-mm&m=125059325722370&w=2 > > I think It's more simple than KOSAKI's idea. > Is any problem in my patch ?
Hmm, I think
1. Anyway, we need turn on PG_mlock. 2. PG_mlock prevent livelock because page_evictable() check is called at very early in shrink_page_list(). -- 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/
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