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Date:   Tue, 21 May 2019 09:06:38 +0200
From:   Oleksandr Natalenko <oleksandr@redhat.com>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Minchan Kim <minchan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tim Murray <timmurray@google.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Daniel Colascione <dancol@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Sonny Rao <sonnyrao@google.com>,
        Brian Geffon <bgeffon@google.com>
Subject: Re: [RFC 4/7] mm: factor out madvise's core functionality
Message-ID: <20190521070638.yhn3w4lpohwcqbl3@butterfly.localdomain>
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Hi.

On Tue, May 21, 2019 at 08:50:00AM +0200, Michal Hocko wrote:
> On Tue 21-05-19 08:36:28, Oleksandr Natalenko wrote:
> [...]
> > Regarding restricting the hints, I'm definitely interested in having
> > remote MADV_MERGEABLE/MADV_UNMERGEABLE. But, OTOH, doing it via remote
> > madvise() introduces another issue with traversing remote VMAs reliably.
> > IIUC, one can do this via userspace by parsing [s]maps file only, which
> > is not very consistent, and once some range is parsed, and then it is
> > immediately gone, a wrong hint will be sent.
> > 
> > Isn't this a problem we should worry about?
> 
> See http://lkml.kernel.org/r/20190520091829.GY6836@dhcp22.suse.cz

Oh, thanks for the pointer.

Indeed, for my specific task with remote KSM I'd go with map_files
instead. This doesn't solve the task completely in case of traversal
through all the VMAs in one pass, but makes it easier comparing to a
remote syscall.

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Senior Software Maintenance Engineer