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Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE_SYMBOL(), cleanup and fixes crash bugs
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: Ingo Molnar <mingo at kernel dot org>, linux-arch at vger dot kernel dot org, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, x86 at kernel dot org, lkml <linux-kernel at vger dot kernel dot org>, "Steven Rostedt (Red Hat)" <rostedt at goodmis dot org>, systemtap at sourceware dot org, "David S. Miller" <davem at davemloft dot net>
- Date: Fri, 20 Dec 2013 13:21:58 +0900
- Subject: Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE_SYMBOL(), cleanup and fixes crash bugs
- Authentication-results: sourceware.org; auth=none
- References: <20131219090353 dot 14309 dot 15496 dot stgit at kbuild-fedora dot novalocal> <y0m38loefhx dot fsf at fche dot csb>
(2013/12/20 5:46), Frank Ch. Eigler wrote:
>
> Hi, Masami -
>
>
> masami.hiramatsu.pt wrote:
>
>> Here is the version 6 of NOKPROBE_SYMBOL series. :)
>> [...]
>
> Some preliminary results from building these on top of tip/master on
> x86-64.
>
> # stap -te "probe kprobe.function("*") {}"
>
> starts up OK, without crashes, which looks like great progress.
That's a good news :)
> But a
> closer look indicates that the insertion of kprobes is taking about
> three (!!) orders of magnitude longer than before, as judged by the
> rate of increase of 'wc -l /sys/kernel/debug/kprobes/list'.
Right, because kprobes are not designed for thousands of probes.
> So, one
> has to let the thing run for several hours just to get all the kprobes
> inserted, never mind letting stress-testing begin.
>
> For reference, here's the steady-state "perf top" output during all this
> insertion work:
>
> 54.81% [kernel] [k] _raw_spin_unlock_irqrestore
> 38.13% [kernel] [k] __slab_alloc
> 1.11% [kernel] [k] kprobe_ftrace_handler
> 0.88% [kernel] [k] _raw_spin_unlock_irq
Hmm, interesting. Those probes are registered as disabled?
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com