linux-kernel - Re: [External] Re: [PATCH v7 00/15] Free some vmemmap pages of hugetlb page

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Message-ID: <CAMZfGtVpTyUfpU7KXY8XZWxpguxLdZ=JmPAyHm4eipQ9o_Z6Bw@mail.gmail.com>
Date:   Tue, 8 Dec 2020 10:26:05 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, dave.hansen@...ux.intel.com,
        hpa@...or.com, x86@...nel.org, bp@...en8.de, mingo@...hat.com,
        Thomas Gleixner <tglx@...utronix.de>,
        pawan.kumar.gupta@...ux.intel.com, mchehab+huawei@...nel.org,
        paulmck@...nel.org, viro@...iv.linux.org.uk,
        Peter Zijlstra <peterz@...radead.org>, luto@...nel.org,
        oneukum@...e.com, jroedel@...e.de,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        anshuman.khandual@....com, Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-doc@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v7 00/15] Free some vmemmap pages of
 hugetlb page

On Tue, Dec 8, 2020 at 2:38 AM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Fri, Dec 04, 2020 at 11:39:31AM +0800, Muchun Song wrote:
> > On Fri, Dec 4, 2020 at 7:49 AM Mike Kravetz <mike.kravetz@...cle.com> wrote:
> > > As previously mentioned, I feel qualified to review the hugetlb changes
> > > and some other closely related changes.  However, this patch set is
> > > touching quite a few areas and I do not feel qualified to make authoritative
> > > statements about them all.  I too hope others will take a look.
> >
> > Agree. I also hope others can take a look at other modules(e.g.
> > sparse-vmemmap, memory-hotplug). Thanks for everyone's efforts
> > on this.
>
> I got sidetracked by some other stuff but I plan to continue reviewing
> this series.

Many thanks, Oscar.

>
> One thing that came to my mind is that if we do as David suggested in
> patch#4, and we move it towards the end to actually __enable__ this
> once all the infrastructure is there (unless hstate->nr_vmemmap_pages
> differs from 0 we should not be doing any work AFAIK), we could also
> move patch#6 to the end (right before the enablement), kill patch#7
> and only leave patch#13.
>
> The reason for that (killing patch#7 and leaving patch#13 only)
> is that it does not make much sense to me to disable PMD-mapped vmemmap
> depending on the CONFIG_HUGETLB_xxxxx as that is enabled by default
> to replace that later by the boot kernel parameter.
> It looks more natural to me to disable it when we introduce the kernel
> boot parameter, before the actual enablement of the feature.

Thanks for your suggestions. I agree with you. :)

>
> As I said, I plan to start the review again, but the order above would
> make more sense to me.
>
> thanks
>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun