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From:   Daniel Colascione <dancol@google.com>
Date:   Tue, 28 May 2019 01:31:13 -0700
Message-ID: <CAKOZuesnS6kBFX-PKJ3gvpkv8i-ysDOT2HE2Z12=vnnHQv0FDA@mail.gmail.com>
Subject: Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER
To:     Minchan Kim <minchan@kernel.org>
Cc:     Michal Hocko <mhocko@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>,
        Shakeel Butt <shakeelb@google.com>,
        Sonny Rao <sonnyrao@google.com>,
        Brian Geffon <bgeffon@google.com>,
        Linux API <linux-api@vger.kernel.org>
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On Tue, May 28, 2019 at 1:14 AM Minchan Kim <minchan@kernel.org> wrote:
> if we went with the per vma fd approach then you would get this
> > feature automatically because map_files would refer to file backed
> > mappings while map_anon could refer only to anonymous mappings.
>
> The reason to add such filter option is to avoid the parsing overhead
> so map_anon wouldn't be helpful.

Without chiming on whether the filter option is a good idea, I'd like
to suggest that providing an efficient binary interfaces for pulling
memory map information out of processes.  Some single-system-call
method for retrieving a binary snapshot of a process's address space
complete with attributes (selectable, like statx?) for each VMA would
reduce complexity and increase performance in a variety of areas,
e.g., Android memory map debugging commands.