From: Ingo Molnar <mingo@elte.hu>
To: David Miller <davem@davemloft.net>
Cc: hch@lst.de, airlied@linux.ie, akpm@linux-foundation.org,
torvalds@linux-foundation.org, ak@suse.de, pq@iki.fi,
jbeulich@novell.com, linux-kernel@vger.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Masami Hiramatsu <mhiramat@redhat.com>
Subject: Re: [PATCH] Revert "x86: optimize page faults like all other achitectures and kill notifier cruft"
Date: Wed, 9 Jan 2008 11:41:49 +0100 [thread overview]
Message-ID: <20080109104149.GB8041@elte.hu> (raw)
In-Reply-To: <20080108.232311.79648776.davem@davemloft.net>
(kprobes folks Cc:-ed)
* David Miller <davem@davemloft.net> wrote:
> From: Christoph Hellwig <hch@lst.de>
> Date: Wed, 9 Jan 2008 08:19:45 +0100
>
> > On Wed, Jan 09, 2008 at 03:55:20AM +0000, Dave Airlie wrote:
> > > now because Linus said send him a patch to revert regressions rather than
> > > just complain,
> >
> > this is not a regression by any definition. You were abusing
> > exported symbols for out of tree junk, so you'll lose.
>
> And furthermore, they don't even need it, use a kprobe.
i agree. There a few practical complication on x86: the do_page_fault()
function is currently excluded from kprobe probing, for recursion
reasons. handle_mm_fault() can be probed OTOH - but that does not catch
vmalloc()-ed faults. The middle of do_page_fault() [line 348] should
work better [the point after notify_page_fault()] - but it's usually
more fragile to insert probes to such middle-of-the-function places.
So probing pagefaults is not as easy as it should/could be. We should
put a practical NOP marker to around line 348, to make it easier (and
faster) for systemtap to probe there.
(__kprobes is a highly confusing newspeak name btw - it should be
__noprobe instead.)
Ingo
next prev parent reply other threads:[~2008-01-09 10:42 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-09 2:34 [PATCH] Revert "x86: optimize page faults like all other achitectures and kill notifier cruft" Dave Airlie
2008-01-09 2:37 ` Andi Kleen
2008-01-09 3:06 ` Andrew Morton
2008-01-09 3:17 ` Dave Airlie
2008-01-09 3:29 ` Andrew Morton
2008-01-09 3:55 ` Dave Airlie
2008-01-09 7:19 ` Christoph Hellwig
2008-01-09 7:23 ` David Miller
2008-01-09 10:41 ` Ingo Molnar [this message]
2008-01-09 16:52 ` Mathieu Desnoyers
2008-01-09 19:07 ` Andi Kleen
2008-01-09 20:01 ` Pekka Paalanen
2008-01-09 20:08 ` Andi Kleen
2008-01-09 4:17 ` Andi Kleen
2008-01-09 9:12 ` Jan Beulich
2008-01-09 15:18 ` Arjan van de Ven
2008-01-09 15:21 ` Andi Kleen
2008-01-09 15:26 ` Ingo Molnar
2008-01-09 7:17 ` Christoph Hellwig
2008-01-09 7:22 ` David Miller
2008-01-09 13:19 ` Jiri Kosina
2008-01-09 13:48 ` David Miller
2008-01-09 14:23 ` Andi Kleen
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