linux-kernel - Re: [PATCH 1/1] Fix number of events displayed in header

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Date:	Tue, 20 Mar 2012 14:51:23 -0500
From:	Ashay Rane <ashay.r@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	David Ahern <dsahern@...il.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-perf-users@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Ashay Rane <ashay.rane@...c.utexas.edu>
Subject: Re: [PATCH 1/1] Fix number of events displayed in header

Hello,

The problem I am seeing is that the `perf record' output does not
comform with the output of `perf stat'. For example, for `hackbench 10
process 1000', I see 19 x 10^9 cycles reported by `perf stat'.
However, `perf report -n' prints "Events: 2K cycles" and `perf report
-n --dso hackbench' prints "Events: 47 cycles".

The difference in the reported counts occurs for PMU events too.

$ perf stat -e cycles ./hackbench 10 process 1000
Running with 10*40 (== 400) tasks.
Time: 4.039

 Performance counter stats for './hackbench 10 process 1000':

    19,060,433,134 cycles                    #    0.000 GHz

       4.078210213 seconds time elapsed

$ perf record -e cycles ./hackbench 10 process 1000
Running with 10*40 (== 400) tasks.
Time: 4.053
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.165 MB perf.data (~7205 samples) ]

$ perf report -n --stdio --dso hackbench
# dso: hackbench
# ========
# captured on: Mon Mar 12 15:14:57 2012
# hostname : iHitch
# os release : 3.2.8-1-ARCH
# perf version : 3.2-3
# arch : x86_64
# nrcpus online : 2
# nrcpus avail : 2
# cpudesc : Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
# cpuid : GenuineIntel,6,23,10
# total memory : 2979384 kB
# cmdline : /usr/bin/perf record -e cycles ./hackbench 10 process 1000
# event : name = cycles, type = 0, config = 0x0, config1 = 0x0,
config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 1611, 1612 }
# HEADER_CPU_TOPOLOGY info available, use -I to display
# HEADER_NUMA_TOPOLOGY info available, use -I to display
# ========
#
# Events: 47  cycles
#
# Overhead  Samples      Command     Symbol
# ........ ..........  .........  .........
#
    56.16%         24  hackbench  receiver
    40.21%         21  hackbench  sender
     3.63%          2  hackbench  write@plt


#
# (For a higher level overview, try: perf report --sort comm,dso)
#

$

2012/3/20 Peter Zijlstra <a.p.zijlstra@...llo.nl>:
> On Tue, 2012-03-20 at 13:46 -0600, David Ahern wrote:
>>
>> Does not seem appropriate to change from number of sample events to
>> period for all event types. This change assumes the event is cycles,
>> cpu-clock or task-clock.
>
> I'm not seeing that assumption. That said, I don't see the point of the
> change either.
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