linux-kernel - Re: [PATCH V3] KSM: allow dedup all tasks memory

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

ср, 14 нояб. 2018 г. в 01:53, Pavel Tatashin <pasha.tatashin@...een.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.