From: David Rientjes <rientjes@google.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michael J Wolf <mjwolf@us.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [RFC][PATCH 2/6] pagewalk: only split huge pages when necessary
Date: Thu, 3 Feb 2011 13:46:26 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.00.1102031343530.1307@chino.kir.corp.google.com> (raw)
In-Reply-To: <1296768812.8299.1644.camel@nimitz>
On Thu, 3 Feb 2011, Dave Hansen wrote:
> > > diff -puN mm/pagewalk.c~pagewalk-dont-always-split-thp mm/pagewalk.c
> > > --- linux-2.6.git/mm/pagewalk.c~pagewalk-dont-always-split-thp 2011-01-27 10:57:02.309914973 -0800
> > > +++ linux-2.6.git-dave/mm/pagewalk.c 2011-01-27 10:57:02.317914965 -0800
> > > @@ -33,19 +33,35 @@ static int walk_pmd_range(pud_t *pud, un
> > >
> > > pmd = pmd_offset(pud, addr);
> > > do {
> > > + again:
> >
> > checkpatch will warn about the indent.
> >
> > > next = pmd_addr_end(addr, end);
> > > - split_huge_page_pmd(walk->mm, pmd);
> > > - if (pmd_none_or_clear_bad(pmd)) {
> > > + if (pmd_none(*pmd)) {
> >
> > Not sure why this has been changed from pmd_none_or_clear_bad(), that's
> > been done even prior to THP.
>
> The bad check will trigger on huge pmds. We can not use it here. We
> can, however, use pmd_none(). The bad check was moved below to where we
> actually dereference the pmd.
>
Ah, right, thanks.
> > > if (walk->pte_hole)
> > > err = walk->pte_hole(addr, next, walk);
> > > if (err)
> > > break;
> > > continue;
> > > }
> > > + /*
> > > + * This implies that each ->pmd_entry() handler
> > > + * needs to know about pmd_trans_huge() pmds
> > > + */
> >
> > Probably needs to be documented somewhere for users of pagewalk?
>
> Probably, but we don't currently have any central documentation for it.
> Guess we could make some, or just ensure that all the users got updated.
> Any ideas where to put it other than the mm_walk struct?
>
I think noting it where struct mm_walk is declared would be best (just a
"/* must handle pmd_trans_huge() */" would be sufficient) although
eventually it might be cleaner to add a ->pmd_huge_entry().
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next prev parent reply other threads:[~2011-02-03 21:46 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-01 0:33 [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics Dave Hansen
2011-02-01 0:33 ` [RFC][PATCH 1/6] count transparent hugepage splits Dave Hansen
2011-02-01 9:58 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-04 21:18 ` Andrea Arcangeli
2011-02-04 21:28 ` Dave Hansen
2011-02-01 0:33 ` [RFC][PATCH 2/6] pagewalk: only split huge pages when necessary Dave Hansen
2011-02-01 10:04 ` Johannes Weiner
2011-02-01 15:03 ` Dave Hansen
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:33 ` Dave Hansen
2011-02-03 21:46 ` David Rientjes [this message]
2011-02-04 17:19 ` Dave Hansen
2011-02-04 21:10 ` Andrea Arcangeli
2011-02-01 0:34 ` [RFC][PATCH 3/6] break out smaps_pte_entry() from smaps_pte_range() Dave Hansen
2011-02-01 10:08 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:40 ` Dave Hansen
2011-02-01 0:34 ` [RFC][PATCH 4/6] pass pte size argument in to smaps_pte_entry() Dave Hansen
2011-02-01 10:09 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-01 0:34 ` [RFC][PATCH 5/6] teach smaps_pte_range() about THP pmds Dave Hansen
2011-02-01 10:11 ` Johannes Weiner
2011-02-01 15:02 ` Dave Hansen
2011-02-01 16:09 ` Andrea Arcangeli
2011-02-03 21:22 ` David Rientjes
2011-02-03 21:34 ` Dave Hansen
2011-02-01 0:34 ` [RFC][PATCH 6/6] have smaps show transparent huge pages Dave Hansen
2011-02-01 10:12 ` Johannes Weiner
2011-02-03 21:22 ` David Rientjes
2011-02-01 15:38 ` [RFC][PATCH 0/6] more detailed per-process transparent hugepage statistics Andrea Arcangeli
2011-02-01 17:15 ` Dave Hansen
2011-02-01 20:39 ` Andrea Arcangeli
2011-02-01 20:56 ` Dave Hansen
2011-02-02 0:07 ` Andrea Arcangeli
2011-02-08 17:54 ` Dave Hansen
2011-02-08 18:17 ` Andrea Arcangeli
2011-02-03 21:54 ` David Rientjes
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