RE: Difference between Oprofile results and Perf results running the same use case

Hi,

One generally wants to look at an application performance when the system does not swap.
In your case, your system seems to be suffering from swapping.

Fix that issue then look at your application performance.
Tune it if needed.
As long as you suffer from swapping, don’t waste your time trying to improve its performance by saving CPU cycles from your app.

My few cents
++Cyrille

From: Sabra Gargouri [mailto:[email protected]]
Sent: Tuesday, September 02, 2014 8:41 PM
To: [email protected]
Subject: Difference between Oprofile results and Perf results running the same use case



Hi,
I would like to profile my system when running my own application , so for that purpose I used Oprofile and also Perf tool. I run separately Oprofile and Perf with the same use case (same application and same duration).
When using Oprofile, I configured opcontrol with --event=CPU_ CYCLES:100000:0:1:1 and for perf , I used -c 100000 to be sure that both tools are sampling with the same event counter.
When generating results for each tool, I noticed a difference in the percentages. Below are results generated with Perf:

# Events: 362K cycles
#
# Overhead  Samples            Command
# ........ ..........  ...............
#
    31.40%     113991         kthreadd
    31.12%     112975          swapper
    11.96%      43418          dvbtest
     7.31%      26539     SE-Aud-Mixer
     4.34%      15750      kworker/0:1
     3.33%      12070            klogd
     3.31%      12033          syslogd
     2.57%       9327   irq/140-vsync0
     1.12%       4058             perf
     0.90%       3258      kworker/1:1
     0.55%       1990   irq/141-vsync1
     0.39%       1414   INF-EvtAsyncCb
     0.35%       1270      rcu_preempt
     0.31%       1108        VIB-Hpd/0
     0.21%        768      ksoftirqd/0
     0.19%        688             sshd
     0.14%        498            udevd
     0.11%        416            pkill
     0.11%        403     kworker/u4:0
     0.04%        138       INP-FE-IP1
     0.04%        136       INP-FE-IP0
     0.03%        127       INP-FE-IP5
     0.03%        121       INP-FE-IP2
     0.03%        118       INP-FE-IP3
     0.03%        107     ICS-Watchdog
     0.03%        106       INP-FE-IP4
     0.03%        101  VIB-HdmiRxMonit
     0.01%         40             init
     0.00%         11      ksoftirqd/1
     0.00%          8            dtach
     0.00%          6          rpcbind
     0.00%          2         ICS-Nsrv
     0.00%          2              :36
     0.00%          1        ICS-Admin
and here after results generated with Oprofile :

CPU_CYCLES:100000|
  samples|      %|
------------------
  1492238 76.8928 vmlinux
   230774 11.8914 libc-2.14.1.so
   107878  5.5588 dvbtest
    55578  2.8639 player2
    16198  0.8347 oprofiled
    15934  0.8211 mme
     7958  0.4101 stmcore_display_stiH407
     3226  0.1662 ics
     1975  0.1018 libpthread-2.14.1.so
     1547  0.0797 sth264pp
     1155  0.0595 ksound
     1107  0.0570 libcrypto.so.1.0.0
      899  0.0463 stm_event
      832  0.0429 syslogd
      466  0.0240 klogd
      445  0.0229 ld-2.14.1.so
      428  0.0221 strelayfs
      416  0.0214 bash
      378  0.0195 stm_wrapper
      238  0.0123 stlinuxtv
      206  0.0106 stm_registry
      182  0.0094 stm_pixel_capture
      140  0.0072 displaylink
      131  0.0068 stm_memsrcsink
      101  0.0052 stm_fe_ip
       52  0.0027 sshd
       37  0.0019 vibe_os
       24  0.0012 hdmirx_stiH407
       22  0.0011 libprocps.so.1.1.0
       22  0.0011 osdev_abs
       20  0.0010 ophelp
       15 7.7e-04 gawk
       15 7.7e-04 udevd
        6 3.1e-04 libnss_files-2.14.1.so
        4 2.1e-04 pkill
        3 1.5e-04 grep
        3 1.5e-04 sleep
        3 1.5e-04 libm-2.14.1.so
        3 1.5e-04 init
        2 1.0e-04 libgcc_s-4.8.2.so.1
        2 1.0e-04 libresolv-2.14.1.so
        2 1.0e-04 libpopt.so.0.0.0
        2 1.0e-04 libtirpc.so.1.0.10
        1 5.2e-05 rm
        1 5.2e-05 seq
        1 5.2e-05 libbfd-2.23.2.so
        1 5.2e-05 libgmp.so.10.1.3
        1 5.2e-05 libwrap.so.0.7.6

My focus is on "dvbtest" application. As you see in the results, Oprofile shows 5.558% against 11.96% with Perf.
Why results are so different?

PS: I used Oprofile 0.97 version, because it's the version available in the environment where I have to test and could not use the versions later.

Regards,

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