linux-kernel - Re: [External] Re: [PATCH v9 11/11] mm/hugetlb: Optimize the code with the help of the compiler

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Message-ID: <CAMZfGtUesG88wnwN6XEXWSyDFgWFGqNS153sUkXqxZu-U0h9DA@mail.gmail.com>
Date:   Thu, 17 Dec 2020 18:42:02 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
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>,
        Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        David Hildenbrand <david@...hat.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 v9 11/11] mm/hugetlb: Optimize the code
 with the help of the compiler

On Thu, Dec 17, 2020 at 6:32 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Sun, Dec 13, 2020 at 11:45:34PM +0800, Muchun Song wrote:
> >  static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
> >  {
> > -     return h->nr_free_vmemmap_pages;
> > +     return h->nr_free_vmemmap_pages && is_power_of_2(sizeof(struct page));
>
> This is wrong as it will return either true or false, but not what we want:

Yeah, very thanks for pointing that out.

>
>         static inline unsigned long free_vmemmap_pages_size_per_hpage(struct hstate *h)
>         {
>                 return (unsigned long)free_vmemmap_pages_per_hpage(h) << PAGE_SHIFT;
>         }
>
> the above will compute to 4096, which is wrong for obvious reasons.

You are right. It is my mistake. Thanks Oscar.

>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun