linux-kernel - Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE

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Date:	Fri, 20 Dec 2013 13:21:58 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-arch@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>, x86@...nel.org,
	lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	systemtap@...rceware.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH -tip v6 00/22] kprobes: introduce NOKPROBE_SYMBOL(), cleanup
 and fixes crash bugs

(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@...achi.com


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