From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Stephane Eranian <eranian@google.com>,
David Ahern <dsahern@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"mingo@elte.hu" <mingo@elte.hu>,
"ak@linux.intel.com" <ak@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Jiri Olsa <jolsa@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions
Date: Wed, 9 Oct 2013 12:39:32 +0200 [thread overview]
Message-ID: <20131009103932.GB3081@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20131009095906.GB17480@gmail.com>
On Wed, Oct 09, 2013 at 11:59:06AM +0200, Ingo Molnar wrote:
> PeterZ didn't like exposing the physical RAM address, right?
More than not like; its useless and broken, see below.
> Peter: could we expose the page frame number instead? (Maybe mix it with a
> random seed through the hash-mixer and expose that.) User-space will thus
> be able to discover whether two pages are shared or not, but not extract
> other information.
No, all physical stuff is useless, a page can get moved about through
swap/ksm/thp/compaction/etc.
> The global MM ID thing looked rather ugly as well.
I'm still having the argument with Stephane -- although it fell off-list
-- on why this wouldn't work.
AFAICT the mm_id should work for CLONE_VM, as CLONE_VM inherits the
entire address space so all should be identical when mm_id match.
> That way we could drop the inode info as well? That feels a bit hacky too.
No, the inode stuff is required for shared pages, its the only way to
track them; and barring a filename (which we've so far used for this)
the dev:ino:gen thing is the only way to uniquely identify files -- it
even works where filenames don't, eg. filesystem namespaces and weird
things like shm that don't have stable filenames.
prev parent reply other threads:[~2013-10-09 10:39 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-30 15:44 Stephane Eranian
2013-09-30 16:15 ` Peter Zijlstra
2013-09-30 16:48 ` Stephane Eranian
2013-09-30 16:54 ` Peter Zijlstra
2013-10-01 11:22 ` Stephane Eranian
2013-10-02 11:23 ` Peter Zijlstra
2013-10-02 11:58 ` Peter Zijlstra
2013-10-02 12:39 ` Ingo Molnar
2013-10-02 12:46 ` Peter Zijlstra
2013-10-02 12:59 ` Stephane Eranian
2013-10-02 13:01 ` Peter Zijlstra
2013-10-02 13:13 ` Stephane Eranian
2013-10-02 13:37 ` Peter Zijlstra
2013-10-02 17:14 ` Kees Cook
2013-10-02 17:20 ` Stephane Eranian
2013-10-02 17:29 ` Kees Cook
2013-10-02 17:49 ` Stephane Eranian
2013-10-02 18:10 ` Kees Cook
2013-10-02 19:00 ` Peter Zijlstra
2013-10-02 19:38 ` Kees Cook
2013-10-02 20:31 ` Peter Zijlstra
2013-10-03 8:55 ` Stephane Eranian
2013-10-03 9:03 ` Peter Zijlstra
2013-10-03 9:13 ` Stephane Eranian
2013-10-03 15:34 ` Kees Cook
2013-10-07 21:04 ` Stephane Eranian
2013-10-08 6:54 ` Peter Zijlstra
2013-10-08 7:15 ` Stephane Eranian
2013-10-08 9:36 ` Peter Zijlstra
2013-10-08 9:42 ` Stephane Eranian
2013-10-08 9:54 ` Peter Zijlstra
2013-10-03 18:32 ` Andi Kleen
2013-10-07 11:16 ` Stephane Eranian
2013-10-07 11:32 ` Peter Zijlstra
2013-10-02 15:22 ` Ingo Molnar
2013-10-08 14:23 ` David Ahern
2013-10-08 19:41 ` Ingo Molnar
2013-10-08 19:54 ` Stephane Eranian
2013-10-08 19:57 ` David Ahern
2013-10-09 9:54 ` Ingo Molnar
2013-10-09 9:59 ` Ingo Molnar
2013-10-09 10:39 ` Peter Zijlstra [this message]
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