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64 lines
3.5 KiB
64 lines
3.5 KiB
Demonstrations of vfsreadlat.py, the Linux eBPF/bcc version.
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This example traces the latency of vfs_read (time from call to return), printing
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it as a histogram distribution. By default, output is every five seconds:
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# ./vfsreadlat.py
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Tracing... Hit Ctrl-C to end.
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usecs : count distribution
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0 -> 1 : 4457 |*************************************+|
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2 -> 3 : 447 |*** |
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4 -> 7 : 2059 |***************** |
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8 -> 15 : 1179 |********** |
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16 -> 31 : 63 | |
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32 -> 63 : 0 | |
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64 -> 127 : 2 | |
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128 -> 255 : 0 | |
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256 -> 511 : 3 | |
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512 -> 1023 : 1 | |
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1024 -> 2047 : 3 | |
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2048 -> 4095 : 2 | |
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4096 -> 8191 : 0 | |
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8192 -> 16383 : 0 | |
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16384 -> 32767 : 0 | |
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32768 -> 65535 : 0 | |
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65536 -> 131071 : 4 | |
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131072 -> 262143 : 2 | |
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262144 -> 524287 : 0 | |
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524288 -> 1048575 : 4 | |
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^C
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usecs : count distribution
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0 -> 1 : 241 |*************************************+|
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2 -> 3 : 17 |** |
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4 -> 7 : 2 | |
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8 -> 15 : 4 | |
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16 -> 31 : 2 | |
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32 -> 63 : 0 | |
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64 -> 127 : 1 | |
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128 -> 255 : 0 | |
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256 -> 511 : 1 | |
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512 -> 1023 : 1 | |
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1024 -> 2047 : 0 | |
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2048 -> 4095 : 1 | |
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4096 -> 8191 : 0 | |
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8192 -> 16383 : 0 | |
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16384 -> 32767 : 0 | |
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32768 -> 65535 : 0 | |
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65536 -> 131071 : 0 | |
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131072 -> 262143 : 0 | |
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262144 -> 524287 : 0 | |
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524288 -> 1048575 : 1 | |
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These examples show outliers in the 524 - 1048 milliseconds range. Since
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vfs_read() will catch many types of events, this could be anything including
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keystroke latency on ssh sessions. Further drilling with bcc will be necessary
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to identify more details.
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Full usage:
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# ./vfsreadlat.py -h
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USAGE: ./vfsreadlat.py [interval [count]]
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