| Server IP : 216.250.13.251 / Your IP : 216.73.216.164 Web Server : nginx/1.24.0 System : Linux gunay 6.8.0-134-generic #134-Ubuntu SMP PREEMPT_DYNAMIC Fri Jun 26 18:43:11 UTC 2026 x86_64 User : root ( 0) PHP Version : 7.4.33 Disable Function : pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_get_handler,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,pcntl_async_signals,pcntl_unshare, MySQL : OFF | cURL : ON | WGET : ON | Perl : ON | Python : OFF | Sudo : ON | Pkexec : OFF Directory : /usr/share/doc/bpftrace/examples/ |
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Demonstrations of biolatency, the Linux BPF/bpftrace version. This traces block I/O, and shows latency as a power-of-2 histogram. For example: # ./biolatency-kp.bt Attaching 3 probes... Tracing block device I/O... Hit Ctrl-C to end. ^C @usecs: [256, 512) 2 | | [512, 1K) 10 |@ | [1K, 2K) 426 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [2K, 4K) 230 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [4K, 8K) 9 |@ | [8K, 16K) 128 |@@@@@@@@@@@@@@@ | [16K, 32K) 68 |@@@@@@@@ | [32K, 64K) 0 | | [64K, 128K) 0 | | [128K, 256K) 10 |@ | While tracing, this shows that 426 block I/O had a latency of between 1K and 2K usecs (1024 and 2048 microseconds), which is between 1 and 2 milliseconds. There are also two modes visible, one between 1 and 2 milliseconds, and another between 8 and 16 milliseconds: this sounds like cache hits and cache misses. There were also 10 I/O with latency 128 to 256 ms: outliers. Other tools and instrumentation, like biosnoop.bt, can shed more light on those outliers. There is another version of this tool in bcc: https://github.com/iovisor/bcc The bcc version provides options to customize the output. "biolatency.bt" is an updated version of "biolatency-kp.bt" and does basically the same thing utilizing the tracepoints instead of kprobes.