| Demonstrations of klockstat, the Linux eBPF/bcc version. |
| |
| klockstat traces kernel mutex lock events and display locks statistics |
| |
| # klockstat.py |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| psi_avgs_work+0x2e 3675 5 5468 18379 |
| flush_to_ldisc+0x22 2833 2 4210 5667 |
| n_tty_write+0x30c 3914 1 3914 3914 |
| isig+0x5d 2390 1 2390 2390 |
| tty_buffer_flush+0x2a 1604 1 1604 1604 |
| commit_echoes+0x22 1400 1 1400 1400 |
| n_tty_receive_buf_common+0x3b9 1399 1 1399 1399 |
| |
| Caller Avg Hold Count Max hold Total hold |
| flush_to_ldisc+0x22 42558 2 76135 85116 |
| psi_avgs_work+0x2e 14821 5 20446 74106 |
| n_tty_receive_buf_common+0x3b9 12300 1 12300 12300 |
| n_tty_write+0x30c 10712 1 10712 10712 |
| isig+0x5d 3362 1 3362 3362 |
| tty_buffer_flush+0x2a 3078 1 3078 3078 |
| commit_echoes+0x22 3017 1 3017 3017 |
| |
| |
| Every caller to using kernel's mutex is displayed on every line. |
| |
| First portion of lines show the lock acquiring data, showing the |
| amount of time it took to acquired given lock. |
| |
| 'Caller' - symbol acquiring the mutex |
| 'Average Spin' - average time to acquire the mutex |
| 'Count' - number of times mutex was acquired |
| 'Max spin' - maximum time to acquire the mutex |
| 'Total spin' - total time spent in acquiring the mutex |
| |
| Second portion of lines show the lock holding data, showing the |
| amount of time it took to hold given lock. |
| |
| 'Caller' - symbol holding the mutex |
| 'Average Hold' - average time mutex was held |
| 'Count' - number of times mutex was held |
| 'Max hold' - maximum time mutex was held |
| 'Total hold' - total time spent in holding the mutex |
| |
| This works by tracing mutex_lock/unlock kprobes, updating the |
| lock stats in maps and processing them in the python part. |
| |
| |
| An -i option can be used to display stats in interval (5 seconds in example below): |
| |
| # klockstat.py -i 5 |
| Tracing lock events... Hit Ctrl-C to end. |
| |
| Caller Avg Spin Count Max spin Total spin |
| psi_avgs_work+0x2e 3822 15 5650 57338 |
| flush_to_ldisc+0x22 4630 1 4630 4630 |
| work_fn+0x4f 4185 1 4185 4185 |
| |
| Caller Avg Hold Count Max hold Total hold |
| psi_avgs_work+0x2e 12155 15 15739 182329 |
| flush_to_ldisc+0x22 13809 1 13809 13809 |
| work_fn+0x4f 5274 1 5274 5274 |
| |
| Caller Avg Spin Count Max spin Total spin |
| psi_avgs_work+0x2e 3715 17 4374 63163 |
| |
| Caller Avg Hold Count Max hold Total hold |
| psi_avgs_work+0x2e 13141 17 19510 223399 |
| ^C |
| |
| |
| A -p option can be used to trace only selected process: |
| |
| # klockstat.py -p 883 |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| pipe_wait+0xa9 625 412686 16930 258277958 |
| pipe_read+0x3f 420 413425 16872 174017649 |
| pipe_write+0x35 471 413425 16765 194792253 |
| |
| Caller Avg Hold Count Max hold Total hold |
| pipe_read+0x3f 473 413425 20063 195773647 |
| pipe_wait+0xa9 604 412686 16972 249598153 |
| pipe_write+0x35 481 413425 16944 199008064 |
| |
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| A -c option can be used to display only callers with specific substring: |
| |
| # klockstat.py -c pipe_ |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| pipe_read+0x3f 422 469554 18665 198354705 |
| pipe_wait+0xa9 679 469536 17196 319017069 |
| pipe_write+0x35 469 469554 17057 220338525 |
| |
| Caller Avg Hold Count Max hold Total hold |
| pipe_write+0x35 638 469554 17330 299857180 |
| pipe_wait+0xa9 779 469535 16912 366047392 |
| pipe_read+0x3f 575 469554 13251 270005394 |
| |
| |
| An -n option can be used to display only specific number of callers: |
| |
| # klockstat.py -n 3 |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| pipe_read+0x3f 420 334120 16964 140632284 |
| pipe_wait+0xa9 688 334116 16876 229957062 |
| pipe_write+0x35 463 334120 16791 154981747 |
| |
| Caller Avg Hold Count Max hold Total hold |
| flush_to_ldisc+0x22 27754 3 63270 83264 |
| pipe_read+0x3f 571 334120 17123 190976463 |
| pipe_wait+0xa9 759 334115 17068 253747213 |
| |
| |
| An -s option can be used to display number of callers backtrace entries: |
| |
| # klockstat.py -n 1 -s 3 |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| pipe_wait+0xa9 685 811947 17376 556542328 |
| pipe_wait+0xa9 |
| pipe_read+0x206 |
| |
| Caller Avg Hold Count Max hold Total hold |
| flush_to_ldisc+0x22 28145 3 63872 84437 |
| flush_to_ldisc+0x22 |
| process_one_work+0x1b0 |
| |
| |
| Output can be sorted by using -S <fields> option on various |
| fields, the acq_total will force the acquired table to be |
| sorted on 'Total spin' column: |
| |
| # klockstat.py -S acq_total |
| Tracing lock events... Hit Ctrl-C to end. |
| ^C |
| Caller Avg Spin Count Max spin Total spin |
| pipe_wait+0xa9 691 269343 17190 186263983 |
| pipe_write+0x35 464 269351 11730 125205417 |
| pipe_read+0x3f 422 269351 17107 113724697 |
| psi_avgs_work+0x2e 2499 11 4454 27494 |
| flush_to_ldisc+0x22 3111 3 5096 9334 |
| n_tty_write+0x30c 2764 1 2764 2764 |
| isig+0x5d 1287 1 1287 1287 |
| tty_buffer_flush+0x2a 961 1 961 961 |
| commit_echoes+0x22 892 1 892 892 |
| n_tty_receive_buf_common+0x3b9 868 1 868 868 |
| |
| Caller Avg Hold Count Max hold Total hold |
| pipe_wait+0xa9 788 269343 17128 212496240 |
| pipe_write+0x35 637 269351 17209 171596811 |
| pipe_read+0x3f 585 269351 11834 157606323 |
| psi_avgs_work+0x2e 8726 11 19177 95996 |
| flush_to_ldisc+0x22 22158 3 43731 66474 |
| n_tty_write+0x30c 9770 1 9770 9770 |
| n_tty_receive_buf_common+0x3b9 6830 1 6830 6830 |
| isig+0x5d 3114 1 3114 3114 |
| tty_buffer_flush+0x2a 2032 1 2032 2032 |
| commit_echoes+0x22 1616 1 1616 1616 |
