From: Ingo Molnar <mingo@kernel.org>
To: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Colin Cross <ccross@android.com>,
LKML <linux-kernel@vger.kernel.org>,
Kyungmin Park <kmpark@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
John Stultz <john.stultz@linaro.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Dave Hansen <dave.hansen@intel.com>,
Rob Landley <rob@landley.net>,
Andrew Morton <akpm@linux-foundation.org>,
Cyrill Gorcunov <gorcunov@openvz.org>,
David Rientjes <rientjes@google.com>,
Davidlohr Bueso <dave@gnu.org>, Kees Cook <keescook@chromium.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
Michel Lespinasse <walken@google.com>,
Rik van Riel <riel@redhat.com>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Arnd Bergmann <arnd@arndb.de>, Dave Jones <davej@redhat.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Oleg Nesterov <oleg@redhat.com>, Shaohua Li <shli@fusionio.com>,
Sasha Levin <sasha.levin@oracle.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
"list@ebiederm.org:DOCUMENTATION" <linux-doc@vger.kernel.org>,
"list@ebiederm.org:MEMORY MANAGEMENT" <linux-mm@kvack.org>
Subject: Re: [PATCH 2/2] mm: add a field to store names for private anonymous memory
Date: Fri, 12 Jul 2013 11:26:47 +0200 [thread overview]
Message-ID: <20130712092647.GB5315@gmail.com> (raw)
In-Reply-To: <51DFC6AE.3020504@kernel.org>
* Pekka Enberg <penberg@kernel.org> wrote:
> > Once the DSO is full -- equal to your previous anon-exec region being
> > full, you simply mmap a new DSO.
> >
> > Wouldn't that work?
>
> Okay and then whenever 'perf top' sees a non-mapped IP it reloads the
> DSO (if it has changed)?
>
> Yeah, I could see that working. It doesn't solve the problems Ingo
> mentioned which are also important, though.
Well, the JIT profiling case is really special - there we are constructing
code and a symbol table on the fly. Talking to perf via a temporary file
sounds unavoidable (and thus proper), because symbol information on that
level is not something the kernel knows (or should know) about.
I was arguing primarily in the context of the original patch: naming
allocator heaps. Today the kernel makes a few educated guesses about what
each memory area is about, in /proc/*/maps:
34511ac000-34511b0000 r--p 001ac000 08:03 1706770 /usr/lib64/libc-2.15.so
34511b0000-34511b2000 rw-p 001b0000 08:03 1706770 /usr/lib64/libc-2.15.so
34511b2000-34511b7000 rw-p 00000000 00:00 0
7f5bdff94000-7f5be63c1000 r--p 00000000 08:03 1710237 /usr/lib/locale/locale-archive
7f5be63c1000-7f5be63c4000 rw-p 00000000 00:00 0
7f5be63d6000-7f5be63d7000 rw-p 00000000 00:00 0
7fff7677f000-7fff767a0000 rw-p 00000000 00:00 0 [stack]
7fff767dd000-7fff767df000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
... but on any larger app there's lots of anon mmap areas that are ...
anonymous! ;-) User-space could help out a bit by naming them. It's not
like there's many heaps, so the performance overhead aspect is minimal.
In the JIT case we have something different, a 'file IO' abstraction
really: the JIT is generating (writing) new code and associated symbol
records. So using temporary files there is natural and proper and most of
the disadvantages I list don't apply because the sheer volume of new code
generated dillutes the overhead of open()/close(), plus we do need some
space for those symbols so a JIT cannot really expect to be able to run in
a pure readonly environment.
In the allocator/heap case we have a _memory_ abstraction it's just that
we also want to name the heap minimally.
For any finer than vma granularity user-space attributes the kernel cannot
help much, it does not know (and probably should not know) about all
user-space data structures.
Right now I don't see any good way to merge the two. (might be due to lack
of imagination)
Thanks,
Ingo
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next prev parent reply other threads:[~2013-07-12 9:26 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-12 2:34 [PATCH 1/2] mm: rearrange madvise code to allow for reuse Colin Cross
2013-07-12 2:34 ` [PATCH 2/2] mm: add a field to store names for private anonymous memory Colin Cross
2013-07-12 5:39 ` Pekka Enberg
2013-07-12 8:13 ` Peter Zijlstra
2013-07-12 8:17 ` Peter Zijlstra
2013-07-12 8:44 ` Ingo Molnar
2013-07-12 8:55 ` Pekka Enberg
2013-07-12 9:00 ` Peter Zijlstra
2013-07-12 9:15 ` Ingo Molnar
2013-07-12 9:27 ` Peter Zijlstra
2013-07-12 9:40 ` Ingo Molnar
2013-07-12 9:49 ` Peter Zijlstra
2013-07-12 10:01 ` Ingo Molnar
2013-07-12 20:51 ` Colin Cross
2013-09-26 1:24 ` Colin Cross
2013-07-12 8:21 ` Pekka Enberg
2013-07-12 8:55 ` Peter Zijlstra
2013-07-12 9:04 ` Pekka Enberg
2013-07-12 9:14 ` Peter Zijlstra
2013-07-12 9:28 ` Ingo Molnar
2013-07-12 9:26 ` Ingo Molnar [this message]
2013-07-12 9:38 ` Pekka Enberg
2013-07-12 9:45 ` Ingo Molnar
2013-07-12 10:09 ` Peter Zijlstra
2013-07-12 5:43 ` Pekka Enberg
2013-07-12 6:18 ` Colin Cross
2013-07-12 7:03 ` Pekka Enberg
2013-07-12 6:36 ` Dave Hansen
2013-07-12 6:42 ` Colin Cross
2013-07-14 14:11 ` Oleg Nesterov
2013-07-14 19:27 ` Colin Cross
2013-07-14 14:17 ` Oleg Nesterov
2013-07-14 19:34 ` Colin Cross
2013-10-15 1:31 [PATCHv3 1/2] mm: rearrange madvise code to allow for reuse Colin Cross
2013-10-15 1:31 ` [PATCH 2/2] mm: add a field to store names for private anonymous memory Colin Cross
2013-10-15 21:21 ` Andrew Morton
2013-10-15 21:32 ` Dave Hansen
2013-10-15 21:47 ` Colin Cross
2013-10-16 0:33 ` Minchan Kim
2013-10-16 20:00 ` Colin Cross
2013-10-16 20:34 ` Dave Hansen
2013-10-16 20:41 ` Colin Cross
2013-10-17 2:47 ` Minchan Kim
2013-10-30 21:15 ` Colin Cross
2013-11-01 1:30 ` Minchan Kim
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