linux-kernel - Re: [External] Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

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Date:   Fri, 20 Nov 2020 18:42:46 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing
 vmemmap if struct page size is not power of two

On Fri, Nov 20, 2020 at 5:16 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 20.11.20 07:43, Muchun Song wrote:
> > We only can free the unused vmemmap to the buddy system when the
> > size of struct page is a power of two.
> >
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
> > ---
> >   mm/hugetlb_vmemmap.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index c3b3fc041903..7bb749a3eea2 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -671,7 +671,8 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
> >       unsigned int order = huge_page_order(h);
> >       unsigned int vmemmap_pages;
> >
> > -     if (hugetlb_free_vmemmap_disabled) {
> > +     if (hugetlb_free_vmemmap_disabled ||
> > +         !is_power_of_2(sizeof(struct page))) {
> >               pr_info("disable free vmemmap pages for %s\n", h->name);
> >               return;
> >       }
> >
>
> This patch should be merged into the original patch that introduced
> vmemmap freeing.

Oh, yeah. Will do.

>
> --
> Thanks,
>
> David / dhildenb
>


-- 
Yours,
Muchun