linux-kernel - Re: [PATCH 3/6] hugetlb: add free page reporting support

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Message-ID: <CA+2MQi-pxRkaftawN=tMxDT7wWyXuS6ZjofcqK+2fwQ9LHvwfQ@mail.gmail.com>
Date:   Thu, 7 Jan 2021 11:38:04 +0800
From:   Liang Li <liliang324@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Liang Li <liliangleo@...iglobal.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 3/6] hugetlb: add free page reporting support

On Thu, Jan 7, 2021 at 12:08 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Tue 05-01-21 22:49:21, Liang Li wrote:
> > hugetlb manages its page in hstate's free page list, not in buddy
> > system, this patch try to make it works for hugetlbfs. It canbe
> > used for memory overcommit in virtualization and hugetlb pre zero
> > out.
>
> David has layed down some more fundamental questions in the reply to the
> cover letter (btw. can you fix your scripts to send patches and make all
> the patches to be in reply to the cover letter please?). But I would

Do you mean attach the patches in the email for the cover letter ?

> like to point out that this changelog would need to change a lot as
> well. It doesn't explain really what, why and how. E.g. what would any
> guest gain by being able to report free huge pages? What would guarantee
> that the pool is replenished when there is a demand? Can this make the
> fault fail or it just takes more time to be satisfied? Why did you
> decide that the reporting infrastructure should be abused to do the
> zeroying? I do remember Alexander pushing back against that and so you
> should better have a very strong arguments to proceed that way.
>
> I am pretty sure there are more questions to come when more details are
> uncovered.
> --
> Michal Hocko
> SUSE Labs

I will try to add more detail about the aspect you referred to. Thanks!

Liang