226 lines
8.1 KiB
Plaintext
226 lines
8.1 KiB
Plaintext
|
|
------------------------------
|
|
****** perf by examples ******
|
|
------------------------------
|
|
|
|
[ From an e-mail by Ingo Molnar, http://lkml.org/lkml/2009/8/4/346 ]
|
|
|
|
|
|
First, discovery/enumeration of available counters can be done via
|
|
'perf list':
|
|
|
|
titan:~> perf list
|
|
[...]
|
|
kmem:kmalloc [Tracepoint event]
|
|
kmem:kmem_cache_alloc [Tracepoint event]
|
|
kmem:kmalloc_node [Tracepoint event]
|
|
kmem:kmem_cache_alloc_node [Tracepoint event]
|
|
kmem:kfree [Tracepoint event]
|
|
kmem:kmem_cache_free [Tracepoint event]
|
|
kmem:mm_page_free [Tracepoint event]
|
|
kmem:mm_page_free_batched [Tracepoint event]
|
|
kmem:mm_page_alloc [Tracepoint event]
|
|
kmem:mm_page_alloc_zone_locked [Tracepoint event]
|
|
kmem:mm_page_pcpu_drain [Tracepoint event]
|
|
kmem:mm_page_alloc_extfrag [Tracepoint event]
|
|
|
|
Then any (or all) of the above event sources can be activated and
|
|
measured. For example the page alloc/free properties of a 'hackbench
|
|
run' are:
|
|
|
|
titan:~> perf stat -e kmem:mm_page_pcpu_drain -e kmem:mm_page_alloc
|
|
-e kmem:mm_page_free_batched -e kmem:mm_page_free ./hackbench 10
|
|
Time: 0.575
|
|
|
|
Performance counter stats for './hackbench 10':
|
|
|
|
13857 kmem:mm_page_pcpu_drain
|
|
27576 kmem:mm_page_alloc
|
|
6025 kmem:mm_page_free_batched
|
|
20934 kmem:mm_page_free
|
|
|
|
0.613972165 seconds time elapsed
|
|
|
|
You can observe the statistical properties as well, by using the
|
|
'repeat the workload N times' feature of perf stat:
|
|
|
|
titan:~> perf stat --repeat 5 -e kmem:mm_page_pcpu_drain -e
|
|
kmem:mm_page_alloc -e kmem:mm_page_free_batched -e
|
|
kmem:mm_page_free ./hackbench 10
|
|
Time: 0.627
|
|
Time: 0.644
|
|
Time: 0.564
|
|
Time: 0.559
|
|
Time: 0.626
|
|
|
|
Performance counter stats for './hackbench 10' (5 runs):
|
|
|
|
12920 kmem:mm_page_pcpu_drain ( +- 3.359% )
|
|
25035 kmem:mm_page_alloc ( +- 3.783% )
|
|
6104 kmem:mm_page_free_batched ( +- 0.934% )
|
|
18376 kmem:mm_page_free ( +- 4.941% )
|
|
|
|
0.643954516 seconds time elapsed ( +- 2.363% )
|
|
|
|
Furthermore, these tracepoints can be used to sample the workload as
|
|
well. For example the page allocations done by a 'git gc' can be
|
|
captured the following way:
|
|
|
|
titan:~/git> perf record -e kmem:mm_page_alloc -c 1 ./git gc
|
|
Counting objects: 1148, done.
|
|
Delta compression using up to 2 threads.
|
|
Compressing objects: 100% (450/450), done.
|
|
Writing objects: 100% (1148/1148), done.
|
|
Total 1148 (delta 690), reused 1148 (delta 690)
|
|
[ perf record: Captured and wrote 0.267 MB perf.data (~11679 samples) ]
|
|
|
|
To check which functions generated page allocations:
|
|
|
|
titan:~/git> perf report
|
|
# Samples: 10646
|
|
#
|
|
# Overhead Command Shared Object
|
|
# ........ ............... ..........................
|
|
#
|
|
23.57% git-repack /lib64/libc-2.5.so
|
|
21.81% git /lib64/libc-2.5.so
|
|
14.59% git ./git
|
|
11.79% git-repack ./git
|
|
7.12% git /lib64/ld-2.5.so
|
|
3.16% git-repack /lib64/libpthread-2.5.so
|
|
2.09% git-repack /bin/bash
|
|
1.97% rm /lib64/libc-2.5.so
|
|
1.39% mv /lib64/ld-2.5.so
|
|
1.37% mv /lib64/libc-2.5.so
|
|
1.12% git-repack /lib64/ld-2.5.so
|
|
0.95% rm /lib64/ld-2.5.so
|
|
0.90% git-update-serv /lib64/libc-2.5.so
|
|
0.73% git-update-serv /lib64/ld-2.5.so
|
|
0.68% perf /lib64/libpthread-2.5.so
|
|
0.64% git-repack /usr/lib64/libz.so.1.2.3
|
|
|
|
Or to see it on a more finegrained level:
|
|
|
|
titan:~/git> perf report --sort comm,dso,symbol
|
|
# Samples: 10646
|
|
#
|
|
# Overhead Command Shared Object Symbol
|
|
# ........ ............... .......................... ......
|
|
#
|
|
9.35% git-repack ./git [.] insert_obj_hash
|
|
9.12% git ./git [.] insert_obj_hash
|
|
7.31% git /lib64/libc-2.5.so [.] memcpy
|
|
6.34% git-repack /lib64/libc-2.5.so [.] _int_malloc
|
|
6.24% git-repack /lib64/libc-2.5.so [.] memcpy
|
|
5.82% git-repack /lib64/libc-2.5.so [.] __GI___fork
|
|
5.47% git /lib64/libc-2.5.so [.] _int_malloc
|
|
2.99% git /lib64/libc-2.5.so [.] memset
|
|
|
|
Furthermore, call-graph sampling can be done too, of page
|
|
allocations - to see precisely what kind of page allocations there
|
|
are:
|
|
|
|
titan:~/git> perf record -g -e kmem:mm_page_alloc -c 1 ./git gc
|
|
Counting objects: 1148, done.
|
|
Delta compression using up to 2 threads.
|
|
Compressing objects: 100% (450/450), done.
|
|
Writing objects: 100% (1148/1148), done.
|
|
Total 1148 (delta 690), reused 1148 (delta 690)
|
|
[ perf record: Captured and wrote 0.963 MB perf.data (~42069 samples) ]
|
|
|
|
titan:~/git> perf report -g
|
|
# Samples: 10686
|
|
#
|
|
# Overhead Command Shared Object
|
|
# ........ ............... ..........................
|
|
#
|
|
23.25% git-repack /lib64/libc-2.5.so
|
|
|
|
|
|--50.00%-- _int_free
|
|
|
|
|
|--37.50%-- __GI___fork
|
|
| make_child
|
|
|
|
|
|--12.50%-- ptmalloc_unlock_all2
|
|
| make_child
|
|
|
|
|
--6.25%-- __GI_strcpy
|
|
21.61% git /lib64/libc-2.5.so
|
|
|
|
|
|--30.00%-- __GI_read
|
|
| |
|
|
| --83.33%-- git_config_from_file
|
|
| git_config
|
|
| |
|
|
[...]
|
|
|
|
Or you can observe the whole system's page allocations for 10
|
|
seconds:
|
|
|
|
titan:~/git> perf stat -a -e kmem:mm_page_pcpu_drain -e
|
|
kmem:mm_page_alloc -e kmem:mm_page_free_batched -e
|
|
kmem:mm_page_free sleep 10
|
|
|
|
Performance counter stats for 'sleep 10':
|
|
|
|
171585 kmem:mm_page_pcpu_drain
|
|
322114 kmem:mm_page_alloc
|
|
73623 kmem:mm_page_free_batched
|
|
254115 kmem:mm_page_free
|
|
|
|
10.000591410 seconds time elapsed
|
|
|
|
Or observe how fluctuating the page allocations are, via statistical
|
|
analysis done over ten 1-second intervals:
|
|
|
|
titan:~/git> perf stat --repeat 10 -a -e kmem:mm_page_pcpu_drain -e
|
|
kmem:mm_page_alloc -e kmem:mm_page_free_batched -e
|
|
kmem:mm_page_free sleep 1
|
|
|
|
Performance counter stats for 'sleep 1' (10 runs):
|
|
|
|
17254 kmem:mm_page_pcpu_drain ( +- 3.709% )
|
|
34394 kmem:mm_page_alloc ( +- 4.617% )
|
|
7509 kmem:mm_page_free_batched ( +- 4.820% )
|
|
25653 kmem:mm_page_free ( +- 3.672% )
|
|
|
|
1.058135029 seconds time elapsed ( +- 3.089% )
|
|
|
|
Or you can annotate the recorded 'git gc' run on a per symbol basis
|
|
and check which instructions/source-code generated page allocations:
|
|
|
|
titan:~/git> perf annotate __GI___fork
|
|
------------------------------------------------
|
|
Percent | Source code & Disassembly of libc-2.5.so
|
|
------------------------------------------------
|
|
:
|
|
:
|
|
: Disassembly of section .plt:
|
|
: Disassembly of section .text:
|
|
:
|
|
: 00000031a2e95560 <__fork>:
|
|
[...]
|
|
0.00 : 31a2e95602: b8 38 00 00 00 mov $0x38,%eax
|
|
0.00 : 31a2e95607: 0f 05 syscall
|
|
83.42 : 31a2e95609: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax
|
|
0.00 : 31a2e9560f: 0f 87 4d 01 00 00 ja 31a2e95762 <__fork+0x202>
|
|
0.00 : 31a2e95615: 85 c0 test %eax,%eax
|
|
|
|
( this shows that 83.42% of __GI___fork's page allocations come from
|
|
the 0x38 system call it performs. )
|
|
|
|
etc. etc. - a lot more is possible. I could list a dozen of
|
|
other different usecases straight away - neither of which is
|
|
possible via /proc/vmstat.
|
|
|
|
/proc/vmstat is not in the same league really, in terms of
|
|
expressive power of system analysis and performance
|
|
analysis.
|
|
|
|
All that the above results needed were those new tracepoints
|
|
in include/tracing/events/kmem.h.
|
|
|
|
Ingo
|
|
|
|
|