linux-kernel - Re: [PATCHv2] mm/gup: speed up check_and_migrate_cma

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: <CAFgQCTshH=FsJbdf49wD=fgJzvbEqzEW--F3oon1aLc64r=u7w@mail.gmail.com>
Date:   Mon, 24 Jun 2019 13:34:01 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Hubbard <jhubbard@...dia.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        LKML <Linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] mm/gup: speed up check_and_migrate_cma_pages() on huge page

On Mon, Jun 24, 2019 at 1:32 PM Pingfan Liu <kernelfans@...il.com> wrote:
>
> On Mon, Jun 24, 2019 at 12:43 PM Ira Weiny <ira.weiny@...el.com> wrote:
> >
> > On Mon, Jun 24, 2019 at 12:12:41PM +0800, Pingfan Liu wrote:
> > > Both hugetlb and thp locate on the same migration type of pageblock, since
> > > they are allocated from a free_list[]. Based on this fact, it is enough to
> > > check on a single subpage to decide the migration type of the whole huge
> > > page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86,
> > > similar on other archs.
> > >
> > > Furthermore, when executing isolate_huge_page(), it avoid taking global
> > > hugetlb_lock many times, and meanless remove/add to the local link list
> > > cma_page_list.
> > >
> > > Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > Cc: Ira Weiny <ira.weiny@...el.com>
> > > Cc: Mike Rapoport <rppt@...ux.ibm.com>
> > > Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: John Hubbard <jhubbard@...dia.com>
> > > Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
> > > Cc: Christoph Hellwig <hch@....de>
> > > Cc: Keith Busch <keith.busch@...el.com>
> > > Cc: Mike Kravetz <mike.kravetz@...cle.com>
> > > Cc: Linux-kernel@...r.kernel.org
> > > ---
> > >  mm/gup.c | 19 ++++++++++++-------
> > >  1 file changed, 12 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/mm/gup.c b/mm/gup.c
> > > index ddde097..544f5de 100644
> > > --- a/mm/gup.c
> > > +++ b/mm/gup.c
> > > @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
> > >       LIST_HEAD(cma_page_list);
> > >
> > >  check_again:
> > > -     for (i = 0; i < nr_pages; i++) {
> > > +     for (i = 0; i < nr_pages;) {
> > > +
> > > +             struct page *head = compound_head(pages[i]);
> > > +             long step = 1;
> > > +
> > > +             if (PageCompound(head))
> > > +                     step = compound_order(head) - (pages[i] - head);
> >
> > Sorry if I missed this last time.  compound_order() is not correct here.
> For thp, prep_transhuge_page()->prep_compound_page()->set_compound_order().
> For smaller hugetlb,
> prep_new_huge_page()->prep_compound_page()->set_compound_order().
> For gigantic page, prep_compound_gigantic_page()->set_compound_order().
>
> Do I miss anything?
>
Oh, got it. It should be 1<<compound_order(head)
> Thanks,
>   Pingfan
> [...]