From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 8B8026B004D for ; Wed, 19 Aug 2009 09:24:41 -0400 (EDT) Date: Wed, 19 Aug 2009 21:24:20 +0800 From: Wu Fengguang Subject: Re: [RFC] respect the referenced bit of KVM guest pages? Message-ID: <20090819132420.GA6137@localhost> References: <20090816051502.GB13740@localhost> <20090816112910.GA3208@localhost> <20090818234310.A64B.A69D9226@jp.fujitsu.com> <20090819120117.GB7306@localhost> <2f11576a0908190505h6da96280xf67c962aa3f5ba07@mail.gmail.com> <20090819121017.GA8226@localhost> <28c262360908190525i6e56ead0mb8dcb01c3d1a69f1@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <28c262360908190525i6e56ead0mb8dcb01c3d1a69f1@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: KOSAKI Motohiro , Rik van Riel , Jeff Dike , Avi Kivity , Andrea Arcangeli , "Yu, Wilfred" , "Kleen, Andi" , Hugh Dickins , Andrew Morton , Christoph Lameter , Mel Gorman , LKML , linux-mm List-ID: On Wed, Aug 19, 2009 at 08:25:56PM +0800, Minchan Kim wrote: > On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang 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 > >> > > >> > A A A A A A A A A A A A A A A A A A A A A A A A A A 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. > >> > > >> > A A A A A A A A A A A A A PG_mlocked > >> > > >> >> Otherwise vm stastics show strange number. > >> >> > >> >> This patch does that. > >> > > >> > Reviewed-by: Wu Fengguang > >> > >> Thanks. > >> > >> > >> > >> >> Index: b/mm/rmap.c > >> >> =================================================================== > >> >> --- a/mm/rmap.c A A A 2009-08-18 19:48:14.000000000 +0900 > >> >> +++ b/mm/rmap.c A A A 2009-08-18 23:47:34.000000000 +0900 > >> >> @@ -362,7 +362,9 @@ static int page_referenced_one(struct pa > >> >> A A A A * unevictable list. > >> >> A A A A */ > >> >> A A A if (vma->vm_flags & VM_LOCKED) { > >> >> - A A A A A A *mapcount = 1; A /* break early from loop */ > >> >> + A A A A A A *mapcount = 1; A A A A A /* break early from loop */ > >> >> + A A A A A A *vm_flags |= VM_LOCKED; /* for prevent to move active list */ > >> > > >> >> + A A A A A A 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. > > 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 ? No, IMHO your patch is simple and good, while KOSAKI's is more complete :) - the try_set_page_mlocked() rename is suitable - the call to try_set_page_mlocked() is necessary on try_to_unmap() - the "if (VM_LOCKED) referenced = 0" in page_referenced() could cover both active/inactive vmscan I did like your proposed if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && - referenced && page_mapping_inuse(page)) + referenced && page_mapping_inuse(page) + && !(vm_flags & VM_LOCKED)) goto activate_locked; which looks more intuitive and less confusing. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org