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Thomas Richter b6d8b858db perf test: test case 'Setup struct perf_event_attr' fails on s390 on z/vm 
perf test 17 'Setup struct perf_event_attr' fails on s390 z/VM guest,
using linux-next kernel.

Root cause is the fall-back from hardware counter cycles

   perf_event_attr:
    type                             0 (PERF_TYPE_HARDWARE)
    size                             136
    config                           0 (PERF_COUNT_HW_CPU_CYCLES)
    { sample_period, sample_freq }   4000
    sample_type                      IP|TID|TIME|ADDR|PERIOD|DATA_SRC
    read_format                      ID|LOST

which returns -ENOENT on s390 z/VM guest. This causes the code to fall
back to software counter task-clock, as can be seen in the debug output:

  ------------------------------------------------------------
   perf_event_attr:
    type                             1 (PERF_TYPE_SOFTWARE)
    size                             136
    config                           0x1 (PERF_COUNT_SW_TASK_CLOCK) <-here
    { sample_period, sample_freq }   4000
    sample_type                      IP|TID|TIME|ADDR|PERIOD|DATA_SRC
    read_format                      ID|LOST

This succeeds on s390 z/VM guest.

This successful installation of the counter task-clock is not listed in
the expected results and the test case fails.

This is caused by commit eb2eac0c7b ("perf evsel: Fallback to
"task-clock" when not system wide") which introduced fall back from
event 'cycles' to event 'task-clock'.

To fix this on s390 allow event number 0 (cycles) and event number 1
(task-clock) as expected result.

Output before:

  # ./perf test -Fv 17
  17: Setup struct perf_event_attr                                    :
  --- start ---
  running './tests/attr/test-stat-group1'
  unsupp  './tests/attr/test-stat-group1'
  running './tests/attr/test-record-graph-default'
  test limitation '!aarch64'
  excluded architecture list ['aarch64']
  expected config=0, got 1
  FAILED './tests/attr/test-record-graph-default' - match failure
  ---- end ----
  Setup struct perf_event_attr: FAILED!
  #

Output after:

  # ./perf test -F 17
  17: Setup struct perf_event_attr               : Ok
  #

Fixes: eb2eac0c7b ("perf evsel: Fallback to "task-clock" when not system wide")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20231219143235.1075522-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
History 2024-01-04 18:44:53 -03:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.