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Message-ID: <ebf5d7357f194debc3bd6e91e0a8da4202c87653.camel@linux.ibm.com>
Subject: Re: [PATCH v5 01/11] asm-generic/pgtable: Adds generic functions to
 monitor lockless pgtable walks
From:   Leonardo Bras <leonardo@linux.ibm.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Song Liu <songliubraving@fb.com>, Michal Hocko <mhocko@suse.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Keith Busch <keith.busch@intel.com>, linux-mm@kvack.org,
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        Christoph Lameter <cl@linux.com>,
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        Dan Williams <dan.j.williams@intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        linux-arch@vger.kernel.org, Santosh Sivaraj <santosh@fossix.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
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        =?ISO-8859-1?Q?J=E9r=F4me?= Glisse <jglisse@redhat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        kvm-ppc@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Reza Arbab <arbab@linux.ibm.com>,
        Allison Randal <allison@lohutok.net>,
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Date:   Wed, 09 Oct 2019 15:09:41 -0300
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On Fri, 2019-10-04 at 13:28 +0200, Peter Zijlstra wrote:
> > Could you please explain it?
> > I mean, why this breaks tmpfs-thp?
> > Also, why mm_cpumask() is also broken?
>=20
> Because shared pages are not bound by a mm; or does it not share the thp
> state between mappings?

By what I could understand, even though the memory is shared, the
mapping may differ for different processes (i.e. the same physical
memory that is mapped as a hugepage in process A can be mapped as a lot
of smallpages in process B).

Did I miss something here? =20

> And once you (re)figure it out, please write it down. It is a crucial
> bit of the puzzle and needs to be part of the Changelogs.

I am still investing time studying this. More on this later :)

Thanks!

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