linux-kernel - Re: [RFC 4/7] mm: factor out madvise's core functionality

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Date:   Tue, 21 May 2019 09:06:38 +0200
From:   Oleksandr Natalenko <oleksandr@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Murray <timmurray@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Daniel Colascione <dancol@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>
Subject: Re: [RFC 4/7] mm: factor out madvise's core functionality

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