linux-kernel - Re: [PATCH 07/50] mm: Account for a THP NUMA hinting update as one PTE update

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130916161150.GF22421@suse.de>
Date:	Mon, 16 Sep 2013 17:11:50 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/50] mm: Account for a THP NUMA hinting update as one
 PTE update

On Mon, Sep 16, 2013 at 04:54:38PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 16, 2013 at 09:39:59AM -0400, Rik van Riel wrote:
> > On 09/16/2013 08:36 AM, Peter Zijlstra wrote:
> > > On Tue, Sep 10, 2013 at 10:31:47AM +0100, Mel Gorman wrote:
> > >> A THP PMD update is accounted for as 512 pages updated in vmstat.  This is
> > >> large difference when estimating the cost of automatic NUMA balancing and
> > >> can be misleading when comparing results that had collapsed versus split
> > >> THP. This patch addresses the accounting issue.
> > >>
> > >> Signed-off-by: Mel Gorman <mgorman@...e.de>
> > >> ---
> > >>  mm/mprotect.c | 2 +-
> > >>  1 file changed, 1 insertion(+), 1 deletion(-)
> > >>
> > >> diff --git a/mm/mprotect.c b/mm/mprotect.c
> > >> index 94722a4..2bbb648 100644
> > >> --- a/mm/mprotect.c
> > >> +++ b/mm/mprotect.c
> > >> @@ -145,7 +145,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
> > >>  				split_huge_page_pmd(vma, addr, pmd);
> > >>  			else if (change_huge_pmd(vma, pmd, addr, newprot,
> > >>  						 prot_numa)) {
> > >> -				pages += HPAGE_PMD_NR;
> > >> +				pages++;
> > > 
> > > But now you're not counting pages anymore..
> > 
> > The migrate statistics still count pages. That makes sense, since the
> > amount of work scales with the amount of memory moved.
> 
> Right.
> 
> > It is just the "number of faults" counters that actually count the
> > number of faults again, instead of the number of pages represented
> > by each fault.
> 
> So you're suggesting s/pages/faults/ or somesuch?
> 

It's really the number of ptes that are updated.

> > IMHO this change makes sense.
> 
> I never said the change didn't make sense as such. Just that we're no
> longer counting pages in change_*_range().

well, it's still a THP page. Is it worth renaming?

-- 
Mel Gorman
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/