iovisor/bcc

print_log2_hist to strip leading zeros

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#1,109 opened on Apr 12, 2017

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Description

Instead of this:

# ./funclatency vfs_write
Tracing 1 functions for "vfs_write"... Hit Ctrl-C to end.
^C
     nsecs               : count     distribution
         0 -> 1          : 0        |                                        |
         2 -> 3          : 0        |                                        |
         4 -> 7          : 0        |                                        |
         8 -> 15         : 0        |                                        |
        16 -> 31         : 0        |                                        |
        32 -> 63         : 0        |                                        |
        64 -> 127        : 0        |                                        |
       128 -> 255        : 0        |                                        |
       256 -> 511        : 0        |                                        |
       512 -> 1023       : 0        |                                        |
      1024 -> 2047       : 1        |                                        |
      2048 -> 4095       : 400      |*                                       |
      4096 -> 8191       : 4250     |*******************                     |
      8192 -> 16383      : 8652     |****************************************|
     16384 -> 32767      : 4663     |*********************                   |
     32768 -> 65535      : 453      |**                                      |
     65536 -> 131071     : 17       |                                        |
    131072 -> 262143     : 0        |                                        |
    262144 -> 524287     : 0        |                                        |
    524288 -> 1048575    : 0        |                                        |
   1048576 -> 2097151    : 0        |                                        |
   2097152 -> 4194303    : 1        |                                        |
Detaching...

Print this:

# ./funclatency vfs_write
Tracing 1 functions for "vfs_write"... Hit Ctrl-C to end.
^C
     nsecs               : count     distribution
      1024 -> 2047       : 1        |                                        |
      2048 -> 4095       : 400      |*                                       |
      4096 -> 8191       : 4250     |*******************                     |
      8192 -> 16383      : 8652     |****************************************|
     16384 -> 32767      : 4663     |*********************                   |
     32768 -> 65535      : 453      |**                                      |
     65536 -> 131071     : 17       |                                        |
    131072 -> 262143     : 0        |                                        |
    262144 -> 524287     : 0        |                                        |
    524288 -> 1048575    : 0        |                                        |
   1048576 -> 2097151    : 0        |                                        |
   2097152 -> 4194303    : 1        |                                        |
Detaching...

To keep the output more concise. This is especially noticeable by tools that print multiple histograms.

Contributor guide

Research direction
Identify the print log2 hist function implementation (likely in C or Python helper) and modify the output loop to skip rows where count is zero.
Tech stack
cpython
Domain
clibackend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitC or Python programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70