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This patch prints the stddev and hist for the cycles diff of program
block. It can help us to understand if the cycles is noisy or not.
This patch is inspired by Andi Kleen's patch:
https://lwn.net/Articles/600471/
We create new option '--cycles-hist'.
Example:
perf record -b ./div
perf record -b ./div
perf diff -c cycles
# Baseline [Program Block Range] Cycles Diff Shared Object Symbol
# ........ .......................................................... .... ................. ............................
#
46.72% [div.c:40 -> div.c:40] 0 div [.] main
46.72% [div.c:42 -> div.c:44] 0 div [.] main
46.72% [div.c:42 -> div.c:39] 0 div [.] main
20.54% [random_r.c:357 -> random_r.c:394] 1 libc-2.27.so [.] __random_r
20.54% [random_r.c:357 -> random_r.c:380] 0 libc-2.27.so [.] __random_r
20.54% [random_r.c:388 -> random_r.c:388] 0 libc-2.27.so [.] __random_r
20.54% [random_r.c:388 -> random_r.c:391] 0 libc-2.27.so [.] __random_r
17.04% [random.c:288 -> random.c:291] 0 libc-2.27.so [.] __random
17.04% [random.c:291 -> random.c:291] 0 libc-2.27.so [.] __random
17.04% [random.c:293 -> random.c:293] 0 libc-2.27.so [.] __random
17.04% [random.c:295 -> random.c:295] 0 libc-2.27.so [.] __random
17.04% [random.c:295 -> random.c:295] 0 libc-2.27.so [.] __random
17.04% [random.c:298 -> random.c:298] 0 libc-2.27.so [.] __random
8.40% [div.c:22 -> div.c:25] 0 div [.] compute_flag
8.40% [div.c:27 -> div.c:28] 0 div [.] compute_flag
5.14% [rand.c:26 -> rand.c:27] 0 libc-2.27.so [.] rand
5.14% [rand.c:28 -> rand.c:28] 0 libc-2.27.so [.] rand
2.15% [rand@plt+0 -> rand@plt+0] 0 div [.] rand@plt
0.00% [kernel.kallsyms] [k] __x86_indirect_thunk_rax
0.00% [do_mmap+714 -> do_mmap+732] -10 [kernel.kallsyms] [k] do_mmap
0.00% [do_mmap+737 -> do_mmap+765] 1 [kernel.kallsyms] [k] do_mmap
0.00% [do_mmap+262 -> do_mmap+299] 0 [kernel.kallsyms] [k] do_mmap
0.00% [__x86_indirect_thunk_r15+0 -> __x86_indirect_thunk_r15+0] 7 [kernel.kallsyms] [k] __x86_indirect_thunk_r15
0.00% [native_sched_clock+0 -> native_sched_clock+119] -1 [kernel.kallsyms] [k] native_sched_clock
0.00% [native_write_msr+0 -> native_write_msr+16] -13 [kernel.kallsyms] [k] native_write_msr
When we enable the option '--cycles-hist', the output is
perf diff -c cycles --cycles-hist
# Baseline [Program Block Range] Cycles Diff stddev/Hist Shared Object Symbol
# ........ .......................................................... .... ................. ................. ............................
#
46.72% [div.c:40 -> div.c:40] 0 ± 37.8% ▁█▁▁██▁█ div [.] main
46.72% [div.c:42 -> div.c:44] 0 ± 49.4% ▁▁▂█▂▂▂▂ div [.] main
46.72% [div.c:42 -> div.c:39] 0 ± 24.1% ▃█▂▄▁▃▂▁ div [.] main
20.54% [random_r.c:357 -> random_r.c:394] 1 ± 33.5% ▅▂▁█▃▁▂▁ libc-2.27.so [.] __random_r
20.54% [random_r.c:357 -> random_r.c:380] 0 ± 39.4% ▁▁█▁██▅▁ libc-2.27.so [.] __random_r
20.54% [random_r.c:388 -> random_r.c:388] 0 libc-2.27.so [.] __random_r
20.54% [random_r.c:388 -> random_r.c:391] 0 ± 41.2% ▁▃▁▂█▄▃▁ libc-2.27.so [.] __random_r
17.04% [random.c:288 -> random.c:291] 0 ± 48.8% ▁▁▁▁███▁ libc-2.27.so [.] __random
17.04% [random.c:291 -> random.c:291] 0 ±100.0% ▁█▁▁▁▁▁▁ libc-2.27.so [.] __random
17.04% [random.c:293 -> random.c:293] 0 ±100.0% ▁█▁▁▁▁▁▁ libc-2.27.so [.] __random
17.04% [random.c:295 -> random.c:295] 0 ±100.0% ▁█▁▁▁▁▁▁ libc-2.27.so [.] __random
17.04% [random.c:295 -> random.c:295] 0 libc-2.27.so [.] __random
17.04% [random.c:298 -> random.c:298] 0 ± 75.6% ▃█▁▁▁▁▁▁ libc-2.27.so [.] __random
8.40% [div.c:22 -> div.c:25] 0 ± 42.1% ▁▃▁▁███▁ div [.] compute_flag
8.40% [div.c:27 -> div.c:28] 0 ± 41.8% ██▁▁▄▁▁▄ div [.] compute_flag
5.14% [rand.c:26 -> rand.c:27] 0 ± 37.8% ▁▁▁████▁ libc-2.27.so [.] rand
5.14% [rand.c:28 -> rand.c:28] 0 libc-2.27.so [.] rand
2.15% [rand@plt+0 -> rand@plt+0] 0 div [.] rand@plt
0.00% [kernel.kallsyms] [k] __x86_indirect_thunk_rax
0.00% [do_mmap+714 -> do_mmap+732] -10 [kernel.kallsyms] [k] do_mmap
0.00% [do_mmap+737 -> do_mmap+765] 1 [kernel.kallsyms] [k] do_mmap
0.00% [do_mmap+262 -> do_mmap+299] 0 [kernel.kallsyms] [k] do_mmap
0.00% [__x86_indirect_thunk_r15+0 -> __x86_indirect_thunk_r15+0] 7 [kernel.kallsyms] [k] __x86_indirect_thunk_r15
0.00% [native_sched_clock+0 -> native_sched_clock+119] -1 ± 38.5% ▄█▁ [kernel.kallsyms] [k] native_sched_clock
0.00% [native_write_msr+0 -> native_write_msr+16] -13 ± 47.1% ▁█▇▃▁▁ [kernel.kallsyms] [k] native_write_msr
v8:
---
Rebase to perf/core branch
v7:
---
1. v6 got Jiri's ACK.
2. Rebase to latest perf/core branch.
v6:
---
1. Jiri provides better code for using data__hpp_register() in ui_init().
Use this code in v6.
v5:
---
1. Refine the use of data__hpp_register() in ui_init() according to
Jiri's suggestion.
v4:
---
1. Rename the new option from '--noisy' to '--cycles-hist'
2. Remove the option '-n'.
3. Only update the spark value and stats when '--cycles-hist' is enabled.
4. Remove the code of printing '..'.
v3:
---
1. Move the histogram to a separate column
2. Move the svals[] out of struct stats
v2:
---
Jiri got a compile error,
CC builtin-diff.o
builtin-diff.c: In function ‘compute_cycles_diff’:
builtin-diff.c:712:10: error: taking the absolute value of unsigned type ‘u64’ {aka ‘long unsigned int’} has no effect [-Werror=absolute-value]
712 | labs(pair->block_info->cycles_spark[i] -
| ^~~~
Because the result of u64 - u64 is still u64. Now we change the type of
cycles_spark[] to s64.
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20190925011446.30678-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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