linux-kernel - Re: [RFC GIT PULL] perf/trace/lock optimization/scalability improvements

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Date:	Wed, 3 Feb 2010 11:25:41 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul Mackerras <paulus@...ba.org>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>
Subject: Re: [RFC GIT PULL] perf/trace/lock optimization/scalability
	improvements

On Wed, Feb 03 2010, Frederic Weisbecker wrote:
> Hi,
> 
> There are many things that happen in this patchset, treating
> different problems:
> 
> - remove most of the string copy overhead in fast path
> - open the way for lock class oriented profiling (as
>   opposite to lock instance profiling. Both can be useful
>   in different ways).
> - remove the buffers muliplexing (less contention)
> - event injection support
> - remove violent lock events recursion (only 2 among 3, the remaining
>   one is detailed below).
> 
> Some differences, by running:
> 	perf lock record perf sched pipe -l 100000
> 
> Before the patchset:
> 
> 	Total time: 91.015 [sec]
> 
> 	     910.157300 usecs/op
> 		   1098 ops/sec
> 
> After this patchset applied:
> 
> 	Total time: 43.706 [sec]
> 
> 	     437.062080 usecs/op
> 		   2288 ops/sec

This does a lot better here, even if it isn't exactly stellar
performance. It generates a LOT of data:

root@...alem:/dev/shm # time perf lock rec -fg ls
perf.data  perf.data.old
[ perf record: Woken up 0 times to write data ]
[ perf record: Captured and wrote 137.224 MB perf.data (~5995421
samples) ]

real    0m3.320s
user    0m0.000s
sys     0m3.220s

Without -g, it has 1.688s real and 1.590s sys time.

So while this is orders of magnitude better than the previous patchset,
it's still not anywhere near lean. But I expect you know that, just
consider this a 'I tested it and this is what happened' report :-)

-- 
Jens Axboe

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