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base repository: iovisor/bcc
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head repository: brho/bcc
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  • 1 commit
  • 2 files changed
  • 1 contributor

Commits on May 10, 2023

  1. libbpf-tools: use fentry in funclatency 

    For tracing kernel functions, funclatency will attempt to use fentry and
fallback to kprobes if that fails.  I left the option to force the use
of kprobes if you'd like.

Under load, fentry is more efficient:

With kprobes:

cpu:/tmp/b# ./funclatency -u -k bpf_spin_lock
Tracing bpf_spin_lock.  Hit Ctrl-C to exit
^C
     usec                : count    distribution
         0 -> 1          : 565159   |****************************************|
         2 -> 3          : 216204   |***************                         |
         4 -> 7          : 306316   |*********************                   |
         8 -> 15         : 416990   |*****************************           |
        16 -> 31         : 415110   |*****************************           |
        32 -> 63         : 170298   |************                            |
        64 -> 127        : 29726    |**                                      |
       128 -> 255        : 427962   |******************************          |
       256 -> 511        : 233207   |****************                        |
       512 -> 1023       : 453      |                                        |
      1024 -> 2047       : 0        |                                        |
Exiting trace of bpf_spin_lock

With fentry:
cpu:/tmp/b# ./funclatency -u bpf_spin_lock
Tracing bpf_spin_lock.  Hit Ctrl-C to exit
^C
     usec                : count    distribution
         0 -> 1          : 6371351  |****************************************+|
         2 -> 3          : 1100093  |******                                  |
         4 -> 7          : 518197   |***                                     |
         8 -> 15         : 174881   |*                                       |
        16 -> 31         : 25022    |                                        |
        32 -> 63         : 1553     |                                        |
        64 -> 127        : 1312     |                                        |
       128 -> 255        : 2376     |                                        |
       256 -> 511        : 0        |                                        |
Exiting trace of bpf_spin_lock

Signed-off-by: Barret Rhoden <[email protected]>
    @brho
    brho committed May 10, 2023
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