Software Tuning, Performance Optimization & Platform Monitoring
Discussion regarding monitoring and software tuning methodologies, Performance Monitoring Unit (PMU) of Intel microprocessors, and platform updating.

what does "skip" mean in the context of perf test

New Contributor I

perf test

reports on the availability of various functionalities supported by perf in the current environment. 

On one of my machines, I get output that looks like

g32 > perf test
 1: vmlinux symtab matches kallsyms                       : Skip
 2: Detect openat syscall event                           : FAILED!
 3: Detect openat syscall event on all cpus               : FAILED!
 4: Read samples using the mmap interface                 : FAILED!
 5: Test data source output                               : Ok
 6: Parse event definition strings                        : FAILED!
 7: Simple expression parser                              : Ok
 8: PERF_RECORD_* events & perf_sample fields             : Ok
 9: Parse perf pmu format                                 : Ok
10: DSO data read                                         : Ok
11: DSO data cache                                        : Ok
12: DSO data reopen                                       : Ok
13: Roundtrip evsel->name                                 : Ok
14: Parse sched tracepoints fields                        : FAILED!
15: syscalls:sys_enter_openat event fields                : FAILED!
16: Setup struct perf_event_attr                          : Ok
17: Match and link multiple hists                         : Ok
18: 'import perf' in python                               : Ok
19: Breakpoint overflow signal handler                    : Ok
20: Breakpoint overflow sampling                          : Ok
21: Number of exit events of a simple workload            : Skip
22: Software clock events period values                   : Ok

The meaning of "OK" and "FAILED" is clear, but what does "Skip" mean?

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New Contributor III

You can repeat the particular test that was skipped with the verbose option as follows:

perf test -v 1

Here, I've specified the test number 1, which corresponds to the test "vmlinux symtab matches kallsyms." The verbose option can be helpful in understanding the result of a test. If you omit the test number, all tests will be attempted in verbose mode.

Consider test 1 as an example. It may output the following:

Couldn't find a vmlinux that matches the kernel running on this machine, skipping test

The solution is clear now; vmlinux that matches the kernel has to be installed in order to perform the test.

Tests may also be skipped explicitly using the -s command-line option.

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