Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER

From: Minchan Kim <minchan@kernel.org>
To: Daniel Colascione <dancol@google.com>
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>
Subject: Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER
Date: Tue, 28 May 2019 17:49:27 +0900	[thread overview]
Message-ID: <20190528084927.GB159710@google.com> (raw)
In-Reply-To: <CAKOZuesnS6kBFX-PKJ3gvpkv8i-ysDOT2HE2Z12=vnnHQv0FDA@mail.gmail.com>

On Tue, May 28, 2019 at 01:31:13AM -0700, Daniel Colascione wrote:
> 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.

I agree it's the best we can get *generally*.
Michal, any opinion?