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From: Timofey Titovets <timofey.titovets@synesis.ru>
Date: Wed, 14 Nov 2018 02:07:11 +0300
Message-ID: <CAGqmi75sk7A7y=urhyEJ=Wf5Dvv7y48DgPzQP-335s_JV0g+2g@mail.gmail.com>
Subject: Re: [PATCH V3] KSM: allow dedup all tasks memory
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Sender: owner-linux-mm@kvack.org
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To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>, Jann Horn <jannh@google.com>, linux-doc@vger.kernel.org, Linux Kernel <linux-kernel@vger.kernel.org>, linux-mm@kvack.org, Matthew Wilcox <willy@infradead.org>

=D1=81=D1=80, 14 =D0=BD=D0=BE=D1=8F=D0=B1. 2018 =D0=B3. =D0=B2 01:53, Pavel=
 Tatashin <pasha.tatashin@soleen.com>:
>
> > > > That must work, but we out of bit space in vm_flags [1].
> > > > i.e. first 32 bits already defined, and other only accessible only =
on
> > > > 64-bit machines.
> > >
> > > So, grow vm_flags_t to 64-bit, or enable this feature on 64-bit only.
> >
> > With all due respect to you, for that type of things we need
> > mm maintainer opinion.
>
> As far as I understood, you already got directions from the maintainers
> to do similar to the way THP is implemented, and THP uses two flags:
>
> VM_HUGEPAGE VM_NOHUGEPAGE, the same as I am thinking ksm should do if we
> honor MADV_UNMERGEABLE.
>
> When VM_NOHUGEPAGE is set khugepaged ignores those VMAs.
>
> There may be a way to add VM_UNMERGEABLE without extending the size of
> vm_flags, but that would be a good start point in looking how to add a
> new flag.
>
> Again, you could simply enable this feature on 64-bit only.
>
> Pasha
>

Deal!
I will try with only on 64bit machines.