【发布时间】：2012-07-27 23:21:33
【问题描述】：
我正在尝试使用 mutrace 在我的程序中测量互斥量争用，但我不知道如何使用它输出的报告。
mutrace: Showing statistics for process test (PID: 5924).
mutrace: 1223 mutexes used.
Mutex #362 (0x0x1a23750) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #390 (0x0x1a23ac0) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #965 (0x0x1a3a600) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #502 (0x0x1abbc90) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #241 (0x0x7fb6af9019c0) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_lock+0x116) [0x7fb6b1412da6]
/lib/libgcc_s.so.1(_Unwind_Find_FDE+0x2a) [0x7fb6af6fe3ea]
[(nil)]
Mutex #704 (0x0x7fb6afe85020) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_lock+0x116) [0x7fb6b1412da6]
/usr/lib/libstdc++.so.6(_ZNSt6localeC1Ev+0x2f) [0x7fb6afbf021f]
Mutex #452 (0x0x1a240b0) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #981 (0x0x1a3a770) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test() [0x500042]
Mutex #626 (0x0x73daa8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test(_ZN7threads5mutexC2Eb+0x5e) [0x50675e]
Mutex #801 (0x0x1ab6798) first referenced by:
/usr/local/lib/libmutrace.so(pthread_mutex_init+0x1b2) [0x7fb6b14129b4]
./test(_ZN7threads5mutexC1Eb+0x5e) [0x50643e]
mutrace: Showing 10 mutexes in order of (write) contention count:
Mutex # Locked Changed Cont. cont.Time[ms] tot.Time[ms] avg.Time[ms] Flags
362 517216 163871 70638 619.184 138.933 0.000 M-.--.
390 180589 61197 31681 5926.827 463.255 0.003 M-.--.
965 38679 24052 10646 661.639 718.836 0.019 M-.--.
502 35394 19012 1540 153.286 134.116 0.004 M-.--.
241 3481 2715 1378 135.624 1.189 0.000 M-.--.
704 20902 3879 70 0.594 6.702 0.000 M-.--.
452 892 158 49 21.401 125.918 0.141 M-.--.
981 2369 2361 12 0.229 12.984 0.005 M-.--.
626 598 270 4 0.139 8.417 0.014 Mx.r-.
801 125 2 1 0.012 0.270 0.002 Mx.r-.
... ... ... ... ... ... ... ||||||
/|||||
Object: M = Mutex, W = RWLock /||||
State: x = dead, ! = inconsistent /|||
Use: R = used in realtime thread /||
Mutex Type: r = RECURSIVE, e = ERRORCHECK, a = ADAPTIVE /|
Mutex Protocol: i = INHERIT, p = PROTECT /
RWLock Kind: r = PREFER_READER, w = PREFER_WRITER, W = PREFER_WRITER_NONREC
mutrace: Note that rwlocks are shown as two lines: write locks then read locks.
mutrace: Note that the flags column R is only valid in --track-rt mode!
mutrace: 275 condition variables used.
Condvar #235 (0x0x7fb6a039d5c8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #153 (0x0x7fb6a8259978) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #42 (0x0x7fb6a03e8188) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #222 (0x0x7fb6a019b7c8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #118 (0x0x7fb6a0223ca8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #8 (0x0x7fb6a820d748) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #171 (0x0x7fb69c04d9d8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #0 (0x0x7fb69c22a2e8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #75 (0x0x7fb6a81a65f8) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
Condvar #142 (0x0x7fb6a001c308) first referenced by:
/usr/local/lib/libmutrace.so(pthread_cond_init+0x120) [0x7fb6b14134be]
./test(_ZN7threads4condC1Ev+0x17) [0x5051b7]
mutrace: Showing 10 condition variables in order of wait contention count:
Cond # Waits Signals Cont. tot.Time[ms] cont.Time[ms] avg.Time[ms] Flags
235 271 0 0 1370.469 0.000 0.000 x.
153 190 0 0 960.142 0.000 0.000 x.
42 65 0 0 328.264 0.000 0.000 x.
222 52 0 0 262.584 0.000 0.000 x.
118 51 0 0 261.869 0.000 0.000 x.
8 48 0 0 242.422 0.000 0.000 x.
171 41 0 0 207.044 0.000 0.000 x.
0 38 0 0 191.881 0.000 0.000 x.
75 37 0 0 186.835 0.000 0.000 x.
142 35 0 0 176.704 0.000 0.000 x.
... ... ... ... ... ... ... ||
/|
State: x = dead, ! = inconsistent /
Use: R = used in realtime thread
mutrace: Note that the flags column R is only valid in --track-rt mode!
mutrace: Total runtime is 3701.228 ms.
mutrace: Results for SMP with 8 processors.
看来我肯定有互斥争用问题，但我不知道如何将其与我的源代码相关联。我希望有比这更好的回溯。
已根据 mutrace 的网站使用 -rdynamic 编译了可执行文件（以及 -g -gdb 也是）。
我在 stackoverflow 上发现了 mutrace，所以希望有一些有经验的人！
谢谢。
【问题讨论】：
-
短版：遍历输出中出现的每个互斥锁。考虑一下该互斥体的作用以及您可以合理预期的争用量。对于任何显示比您合理预期的更多争用的互斥锁，请确定该争用是否重要，如果是，请分析该互斥锁的使用情况，看看是否有一些简单的方法可以最大限度地减少争用。
-
是的，但是使用如此有限的回溯，我如何确定哪个互斥锁是哪个？显然它正在使用地址，但这不是我以前必须做的事情。我该怎么办？
-
我不确定你为什么得到如此有限的回溯。最坏的情况是，您可以添加代码来记录互斥锁的地址。
标签： c++ multithreading profiling pthreads contention