linux-kernel - Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE

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Date:   Tue, 28 May 2019 01:31:13 -0700
From:   Daniel Colascione <dancol@...gle.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Michal Hocko <mhocko@...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>,
        Shakeel Butt <shakeelb@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER

On Tue, May 28, 2019 at 1:14 AM Minchan Kim <minchan@...nel.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.