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From:   Mina Almasry <almasrymina@google.com>
Date:   Mon, 14 Oct 2019 11:01:26 -0700
Message-ID: <CAHS8izOkcsrCVSu-O2oBVB6NErJmUp+=HC8dDFxZ8fUZt=dgBg@mail.gmail.com>
Subject: Re: [PATCH v5 0/7] hugetlb_cgroup: Add hugetlb_cgroup reservation limits
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
        shuah <shuah@kernel.org>, David Rientjes <rientjes@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        khalid.aziz@oracle.com, open list <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        cgroups@vger.kernel.org,
        =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>
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On Mon, Oct 14, 2019 at 10:33 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 10/11/19 1:41 PM, Mina Almasry wrote:
> > On Fri, Oct 11, 2019 at 12:10 PM Mina Almasry <almasrymina@google.com> wrote:
> >>
> >> On Mon, Sep 23, 2019 at 10:47 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
> >>>
> >>> On 9/19/19 3:24 PM, Mina Almasry wrote:
> >>
> >> Mike, note your suggestion above to check if the page hugetlb_cgroup
> >> is null doesn't work if we want to keep the current counter working
> >> the same: the page will always have a hugetlb_cgroup that points that
> >> contains the old counter. Any ideas how to apply this new counter
> >> behavior to a private NORESERVE mappings? Is there maybe a flag I can
> >> set on the pages at allocation time that I can read on free time to
> >> know whether to uncharge the hugetlb_cgroup or not?
> >
> > Reading the code and asking around a bit, it seems the pointer to the
> > hugetlb_cgroup is in page[2].private. Is it reasonable to use
> > page[3].private to store the hugetlb_cgroup to uncharge for the new
> > counter and increment HUGETLB_CGROUP_MIN_ORDER to 3? I think that
> > would solve my problem. When allocating a private NORESERVE page, set
> > page[3].private to the hugetlb_cgroup to uncharge, then on
> > free_huge_page, check page[3].private, if it is non-NULL, uncharge the
> > new counter on it.
>
> Sorry for not responding sooner.  This approach should work, and it looks like
> you have a v6 of the series.  I'll take a look.
>

Great! Thanks! That's the approach I went with in v6.

> --
> Mike Kravetz