From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Yang Shi <shy828301@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 5/7] khugepaged: Allow to collapse PTE-mapped compound pages
Date: Sat, 28 Mar 2020 15:27:35 +0300 [thread overview]
Message-ID: <20200328122735.nzius2ikvnyvpf2f@box> (raw)
In-Reply-To: <CAHbLzkpV7=EGQVeEEZ_jhpWa-nnVkiZ4_Qa=0KoZCRntprWhgg@mail.gmail.com>
On Fri, Mar 27, 2020 at 06:09:38PM -0700, Yang Shi wrote:
> On Fri, Mar 27, 2020 at 5:34 PM Kirill A. Shutemov <kirill@shutemov.name> wrote:
> >
> > On Fri, Mar 27, 2020 at 11:53:57AM -0700, Yang Shi wrote:
> > > On Fri, Mar 27, 2020 at 10:06 AM Kirill A. Shutemov
> > > <kirill@shutemov.name> wrote:
> > > >
> > > > We can collapse PTE-mapped compound pages. We only need to avoid
> > > > handling them more than once: lock/unlock page only once if it's present
> > > > in the PMD range multiple times as it handled on compound level. The
> > > > same goes for LRU isolation and putpack.
> > > >
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > > ---
> > > > mm/khugepaged.c | 41 +++++++++++++++++++++++++++++++----------
> > > > 1 file changed, 31 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > > index b47edfe57f7b..c8c2c463095c 100644
> > > > --- a/mm/khugepaged.c
> > > > +++ b/mm/khugepaged.c
> > > > @@ -515,6 +515,17 @@ void __khugepaged_exit(struct mm_struct *mm)
> > > >
> > > > static void release_pte_page(struct page *page)
> > > > {
> > > > + /*
> > > > + * We need to unlock and put compound page on LRU only once.
> > > > + * The rest of the pages have to be locked and not on LRU here.
> > > > + */
> > > > + VM_BUG_ON_PAGE(!PageCompound(page) &&
> > > > + (!PageLocked(page) && PageLRU(page)), page);
> > > > +
> > > > + if (!PageLocked(page))
> > > > + return;
> > > > +
> > > > + page = compound_head(page);
> > > > dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
> > >
> > > We need count in the number of base pages. The same counter is
> > > modified by vmscan in base page unit.
> >
> > Is it though? Where?
>
> __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken) in
> vmscan.c, here nr_taken is nr_compound(page), so if it is THP the
> number would be 512.
Could you point a particular codepath?
> So in both inc and dec path of collapse PTE mapped THP, we should mod
> nr_compound(page) too.
I disagree. Compound page is represented by single entry on LRU, so it has
to be counted once.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-03-28 12:27 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-27 17:05 [PATCH 0/7] thp/khugepaged improvements and CoW semantics Kirill A. Shutemov
2020-03-27 17:05 ` [PATCH 1/7] khugepaged: Add self test Kirill A. Shutemov
2020-03-27 17:05 ` [PATCH 2/7] khugepaged: Do not stop collapse if less than half PTEs are referenced Kirill A. Shutemov
2020-03-27 17:30 ` Zi Yan
2020-03-27 17:46 ` Yang Shi
2020-03-27 17:05 ` [PATCH 3/7] khugepaged: Drain LRU add pagevec to get rid of extra pins Kirill A. Shutemov
2020-03-27 17:34 ` Zi Yan
2020-03-28 0:20 ` Kirill A. Shutemov
2020-03-27 18:10 ` Yang Shi
2020-03-28 12:18 ` Kirill A. Shutemov
2020-03-30 18:30 ` Yang Shi
2020-03-30 21:38 ` Kirill A. Shutemov
2020-03-27 17:05 ` [PATCH 4/7] khugepaged: Allow to callapse a page shared across fork Kirill A. Shutemov
2020-03-27 18:19 ` Zi Yan
2020-03-27 21:31 ` Yang Shi
2020-03-27 21:44 ` Zi Yan
2020-03-27 17:05 ` [PATCH 5/7] khugepaged: Allow to collapse PTE-mapped compound pages Kirill A. Shutemov
2020-03-27 18:53 ` Yang Shi
2020-03-28 0:34 ` Kirill A. Shutemov
2020-03-28 1:09 ` Yang Shi
2020-03-28 12:27 ` Kirill A. Shutemov [this message]
2020-03-30 18:38 ` Yang Shi
2020-03-27 18:55 ` Zi Yan
2020-03-28 0:39 ` Kirill A. Shutemov
2020-03-28 1:17 ` Zi Yan
2020-03-28 12:33 ` Kirill A. Shutemov
2020-03-30 18:41 ` Yang Shi
2020-03-30 18:50 ` Yang Shi
2020-03-31 14:08 ` Kirill A. Shutemov
2020-04-01 19:45 ` Yang Shi
2020-03-27 20:45 ` Yang Shi
2020-03-28 0:40 ` Kirill A. Shutemov
2020-03-28 1:12 ` Yang Shi
2020-03-27 17:06 ` [PATCH 6/7] thp: Change CoW semantics for anon-THP Kirill A. Shutemov
2020-03-27 20:07 ` Yang Shi
2020-03-28 0:43 ` Kirill A. Shutemov
2020-03-28 1:30 ` Yang Shi
2020-03-27 17:06 ` [PATCH 7/7] khugepaged: Introduce 'max_ptes_shared' tunable Kirill A. Shutemov
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