linux-kernel - Re: [PATCH -tip v11 0/7] kprobes: NOKPROBE_SYMBOL for modules, and scalbility efforts

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Date:	Thu, 9 Jul 2015 12:19:24 +0000 (UTC)
From:	Pratyush Anand <panand@...hat.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -tip v11 0/7] kprobes: NOKPROBE_SYMBOL for modules, and scalbility efforts

Hi Masamai,

Masami Hiramatsu <masami.hiramatsu.pt <at> hitachi.com> writes:

> 
> Hi,
> Here is the version 11 of NOKPROBE_SYMBOL/scalability series.
> This fixes some issues.

I did not had this mail in my inbox and replied through gmane web interface,
but on systemtap mailing list [2]. Copying same reply here, as not sure if
you are subscribed to systemtap mailing list.

If I have not missed then v11 seems the last version posted for this series.
However, I do not see any ACK/NACK for the series. So, I am just curious
that why didn't it got merged into upstream.

It seems a useful series and without these patches system becomes extremely
slow with large number of kprobes enabled.

When I enabled massive kprobes [1] on my ARM64 system without this patch
series, I see "NMI watchdog: BUG: soft lockup" for all CPUs even before all
kprobes are enabled. However, If I use these patches then system is able to
survive and I can see following output for script [1].

real    1m49.734s
user    0m0.000s
sys     0m53.950s
31364 kprobes enabled :-)

I was able to run `usex -e` to load the system, although I see that system
is mostly occupied by kernel (97%).

*  Unix System EXerciser  *  USER SYSTEM IDLE  LOADAVG  TASKS/RUN   TEST TIME  *
*   USEX Version 1.9-36   *    3%   97%    0%   24.58     232/27    000:02:49  *

~Pratyush

[1]
#!/bin/sh
grep ' [tT] ' /proc/kallsyms | fgrep -v '[' | awk '{print $3}' > syms.list
echo 0 > /sys/kernel/debug/tracing/events/enable
echo 0 > /sys/kernel/debug/tracing/events/kprobes/enable
echo > /sys/kernel/debug/tracing/kprobe_events
for i in `cat syms.list`;
do
	echo "p $i" >> /sys/kernel/debug/tracing/kprobe_events ;
done
time echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
num_kprobe=`cat /sys/kernel/debug/tracing/kprobe_events | wc -l`
echo "$num_kprobe kprobes enabled :-)"

[2] http://permalink.gmane.org/gmane.linux.systemtap/23573

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