linux-kernel - Re: Perf trace event parse errors for KVM events

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Date:	Sun, 06 Jun 2010 11:08:31 +0300
From:	Avi Kivity <avi@...hat.com>
To:	rostedt@...dmis.org
CC:	Stefan Hajnoczi <stefanha@...il.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Frederic Weisbecker <fweisbec@...il.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Darren Hart <darren@...art.com>
Subject: Re: Perf trace event parse errors for KVM events

On 06/04/2010 12:57 AM, Steven Rostedt wrote:
> On Tue, 2010-06-01 at 15:39 +0300, Avi Kivity wrote:
>    
>> On 06/01/2010 02:59 PM, Steven Rostedt wrote:
>>      
>    
>> I meant that viewing would be slowed down.  It's an important part of
>> using ftrace!
>>
>> How long does the Python formatter take to process 100k or 1M events?
>>
>>      
> I finally got around to testing this.
>
> I ran a trace on lock_acquire, and traced 1,253,296 events.
>
> I then created a python plugin to analyze the trace:
>
> ----
> def lock_acquire(trace_seq, event):
>      t = ''
>      r = ''
>      if int(event['flags'])&  1:
>          t = 'try'
>      if int(event['flags'])&  2:
>          r = 'read'
>      trace_seq.puts('t %x %s%s%s' % (
>              event['lockdep_addr'], t, r,
>              event['name']))
>
> def register(pevent):
>      pevent.register_event_handler("lock", "lock_acquire", lock_acquire)
> ----
>
> Disclaimer, I'm not a python expert, and I'm sure the above python code
> sucks.
>    

I think Python more or less guarantees your code will suck no matter 
what you do.

> [root@...9 trace-cmd.git]# time ./trace-cmd report -N>/dev/null 2>&1
>
> real	0m4.653s
> user	0m4.234s
> sys	0m0.419s
>
> * -N keeps trace-cmd from loading any plugins.
>
>
> [root@...9 trace-cmd.git]# time PYTHONPATH=`pwd` ./trace-cmd report>/dev/null 2>&1
>
> real	0m53.916s
> user	0m53.047s
> sys	0m0.859s
>
>
> Yes, running a python interpreter is a bit more expensive. It took 4
> seconds to read the million events with plain C, but 53 seconds to read
> it in python.
>
> That said...  This would only affect you if you were writing this to a
> file. I doubt that you would notice this if you were scanning the trace
> with less.
>    

I'm more worried about searching with less.  But a minute for a million 
events isn't that bad.

> Also, I kicked this off in kernelshark, and it made no difference that I
> can see. This is because kernelshark only evaluates the viewable area of
> the screen.
>    

Neat.  Can it also search?  Where can I find it? <googles, finds, gawks>

-- 
error compiling committee.c: too many arguments to function

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