linux-kernel - Re: [PATCH 5/5] have smaps show transparent huge pages

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Date:	Thu, 10 Feb 2011 19:09:24 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael J Wolf <mjwolf@...ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 5/5] have smaps show transparent huge pages

On Thu, Feb 10, 2011 at 03:09:42PM +0000, Mel Gorman wrote:
> On Thu, Feb 10, 2011 at 07:01:55AM -0800, Dave Hansen wrote:
> > On Thu, 2011-02-10 at 11:20 +0000, Mel Gorman wrote:
> > > > @@ -394,6 +395,7 @@ static int smaps_pte_range(pmd_t *pmd, u
> > > >                       spin_lock(&walk->mm->page_table_lock);
> > > >               } else {
> > > >                       smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_SIZE, walk);
> > > > +                     mss->anonymous_thp += HPAGE_SIZE;
> > > 
> > > I should have thought of this for the previous patch but should this be
> > > HPAGE_PMD_SIZE instead of HPAGE_SIZE? Right now, they are the same value
> > > but they are not the same thing.
> > 
> > Probably.  There's also a nice BUG() in HPAGE_PMD_SIZE if the THP config
> > option is off, which is an added bonus.
> > 
> 
> Unless Andrea has an objection, I'd prefer to see HPAGE_PMD_SIZE.

We get there only through pmd_trans_huge, so HPAGE_PMD_SIZE is
certainly more correct, agreed.

I also think this can go in -mm after s/HPAGE_SIZE/HPAGE_PMD_SIZE/ and
after correcting the locking (see other email).

Maybe it'd be cleaner if we didn't need to cast the pmd to pte_t but I
guess this makes things simpler.

Thanks!
Andrea
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