linux-kernel - Re: [External] Re: [PATCH v8 09/12] mm/hugetlb: Add a kernel parameter hugetlb_free

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Message-ID: <CAMZfGtVks41ZXaUgPdLyNqVCRYTvSm5qAN9GM5e0vqJ9YV7NdA@mail.gmail.com>
Date:   Thu, 10 Dec 2020 20:26:28 +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 v8 09/12] mm/hugetlb: Add a kernel
 parameter hugetlb_free_vmemmap

On Thu, Dec 10, 2020 at 7:41 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Thu, Dec 10, 2020 at 11:55:23AM +0800, Muchun Song wrote:
> > +hugetlb_free_vmemmap
> > +     When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables freeing
> > +     unused vmemmap pages associated each HugeTLB page.
>                                       ^^^ with

Thanks.

>
> > -     if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> > +     if (is_hugetlb_free_vmemmap_enabled())
> > +             err = vmemmap_populate_basepages(start, end, node, NULL);
> > +     else if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> >               err = vmemmap_populate_basepages(start, end, node, NULL);
>
> Not sure if joining those in an OR makes se.se

Well, I can do it.

>
> >       else if (boot_cpu_has(X86_FEATURE_PSE))
> >               err = vmemmap_populate_hugepages(start, end, node, altmap);
> > @@ -1610,7 +1613,8 @@ void register_page_bootmem_memmap(unsigned long section_nr,
> >               }
> >               get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
> >
> > -             if (!boot_cpu_has(X86_FEATURE_PSE)) {
> > +             if (!boot_cpu_has(X86_FEATURE_PSE) ||
> > +                 is_hugetlb_free_vmemmap_enabled()) {
>
> I would add a variable at the beginning called "basepages_populated"
> that holds the result of those two conditions.
> I am not sure if it slightly improves the code as the conditions do
> not need to be rechecked, but the readibility a bit.

Agree. The condition does not need to be rechecked.
Will  do in the next version. Thanks.

>
> > +bool hugetlb_free_vmemmap_enabled;
> > +
> > +static int __init early_hugetlb_free_vmemmap_param(char *buf)
> > +{
> > +     if (!buf)
> > +             return -EINVAL;
> > +
> > +     /* We cannot optimize if a "struct page" crosses page boundaries. */
>
> I think this comment belongs to the last patch.
>

Thanks.

>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun