perf : Performance monitoring for the Linux kernel

- about perf

https://perf.wiki.kernel.org/index.php/Tutorial

[root@fc17 ~]# cat /etc/fedora-release Fedora release 17 (Beefy Miracle) [root@fc17 ~]# uname -ri 3.4.0-1.fc17.x86_64 x86_64

install perf via yum

[root@fc17 ~]# yum install perf -y

[ example usage ]

# perf top

you can see which processes affect linux kernel performance.

you could also see the detail of specific process info.

select a process -> type enter




here’s an output of map details.




- perf record and perf repot

record kernel performance into a file

[root@fc17 ~]# perf record -a sleep 5 [ perf record: Woken up 5 times to write data ] [ perf record: Captured and wrote 2.234 MB perf.data (~97596 samples) ]

info is written into perf.data file
.
read that data
“perf report” command reads info from perf.data file.

# perf report Events: 14K cycles                                                               12.32%          swapper  [kernel.kallsyms]                   [k] native_safe_ha  5.25%              dig  ld-2.15.so                          [.] do_lookup_x  2.75%              dig  ld-2.15.so                          [.] strcmp  2.37%           chrome  libflashplayer.so                   [.] 0x00000000003d  1.75%              dig  [kernel.kallsyms]                   [k] clear_page_c  1.66%              dig  [kernel.kallsyms]                   [k] page_fault  1.49%              dig  libc-2.15.so                        [.] __memset_x86_6  1.38%              dig  ld-2.15.so                          [.] _dl_lookup_sym  1.32%   gnome-terminal  libvte2_90.so.9.3200.1              [.] 0x000000000003  1.20%              dig  [kernel.kallsyms]                   [k] unmap_single_v  1.13%              dig  ld-2.15.so                          [.] _dl_relocate_o  0.97%      gnome-shell  r600_dri.so                         [.] 0x000000000005

# perf report --sort=cpu Events: 14K cycles                                                               26.35%  3 25.43%  0 24.50%  1 23.73%  2

- monitor a specific process

check PID you want to monitor

[root@fc17 ~]# ps aux | grep unbound | grep -v grep unbound   1772  0.1  0.1  51596  9884 ?        Ss   00:23   0:03 unbound -c /etc/unbound/unbound.conf

[root@fc17 ~]# perf stat -p 1772 sleep 5 Performance counter stats for process id '1772':       2619.300788 task-clock                #    0.524 CPUs utilized           [100.00%]             2,294 context-switches          #    0.876 K/sec                   [100.00%]               147 CPU-migrations            #    0.056 K/sec                   [100.00%]               252 page-faults               #    0.096 K/sec                       2,104,000,503 cycles                    #    0.803 GHz                     [49.81%]       576,211,571 stalled-cycles-frontend   #   27.39% frontend cycles idle    [49.55%]       702,855,782 stalled-cycles-backend    #   33.41% backend  cycles idle    [49.55%]     1,512,642,754 instructions              #    0.72  insns per cycle                                                     #    0.46  stalled cycles per insn [50.19%]       296,171,521 branches                  #  113.073 M/sec                   [50.45%]        23,773,996 branch-misses             #    8.03% of all branches         [50.45%]       5.001789912 seconds time elapsed

interesting tool.