perf kwork: Implement 'report' subcommand

Implements framework of 'perf kwork report', which is used to report
time properties such as run time and frequency:

Test cases:

  # perf kwork

   Usage: perf kwork [<options>] {record|report}

      -D, --dump-raw-trace  dump raw trace in ASCII
      -f, --force           don't complain, do it
      -k, --kwork <kwork>   list of kwork to profile (irq, softirq, workqueue, etc)
      -v, --verbose         be more verbose (show symbol address, etc)

  # perf kwork report -h

   Usage: perf kwork report [<options>]

      -C, --cpu <cpu>       list of cpus to profile
      -i, --input <file>    input file name
      -n, --name <name>     event name to profile
      -s, --sort <key[,key2...]>
                            sort by key(s): runtime, max, count
      -S, --with-summary    Show summary with statistics
          --time <str>      Time span for analysis (start,stop)

  # perf kwork report

    Kwork Name                     | Cpu  | Total Runtime | Count     | Max runtime   | Max runtime start   | Max runtime end     |
   --------------------------------------------------------------------------------------------------------------------------------
   --------------------------------------------------------------------------------------------------------------------------------

  # perf kwork report -S

    Kwork Name                     | Cpu  | Total Runtime | Count     | Max runtime   | Max runtime start   | Max runtime end     |
   --------------------------------------------------------------------------------------------------------------------------------
   --------------------------------------------------------------------------------------------------------------------------------
    Total count            :         0
    Total runtime   (msec) :     0.000 (0.000% load average)
    Total time span (msec) :     0.000
   --------------------------------------------------------------------------------------------------------------------------------

  # perf kwork report -C 0,100
  Requested CPU 100 too large. Consider raising MAX_NR_CPUS
  Invalid cpu bitmap

  # perf kwork report -s runtime1
    Error: Unknown --sort key: `runtime1'

   Usage: perf kwork report [<options>]

      -C, --cpu <cpu>       list of cpus to profile
      -i, --input <file>    input file name
      -n, --name <name>     event name to profile
      -s, --sort <key[,key2...]>
                            sort by key(s): runtime, max, count
      -S, --with-summary    Show summary with statistics
          --time <str>      Time span for analysis (start,stop)

  # perf kwork report -i perf_no_exist.data
  failed to open perf_no_exist.data: No such file or directory

  # perf kwork report --time 00FFF,
  Invalid time span

Since there are no report supported events, the output is empty.

Briefly describe the data structure:

1. "class" indicates event type. For example, irq and softiq correspond
to different types.

2. "cluster" refers to a specific event corresponding to a type. For
example, RCU and TIMER in softirq correspond to different clusters,
which contains three types of events: raise, entry, and exit.

3. "atom" includes time of each sample and sample of the previous phase.
(For example, exit corresponds to entry, which is used for timehist.)

Committer notes:

- Add {} for multiline if blocks.

- report_print_work() should either return that ret variable that
  accounts how many bytes were printed or stop accounting and be void.
  Do the former for now to avoid this:

builtin-kwork.c:534:6: error: variable 'ret' set but not used [-Werror,-Wunused-but-set-variable]
        int ret = 0;
            ^
1 error generated.

  When building with:

  ⬢[acme@toolbox perf]$ clang --version
  clang version 13.0.0 (https://github.com/llvm/llvm-project e8991caea8690ec2d17b0b7e1c29bf0da6609076)

Also:

  -       if ((dst_type >= 0) && (dst_type < KWORK_TRACE_MAX)) {
  +       if (dst_type < KWORK_TRACE_MAX) {

Several versions of clang and at least this gcc:

   3    51.40 alpine:3.9                    : FAIL gcc version 8.3.0 (Alpine 8.3.0)
    builtin-kwork.c:411:16: error: comparison of unsigned enum expression >= 0 is
          always true [-Werror,-Wtautological-compare]
            if ((dst_type >= 0) && (dst_type < KWORK_TRACE_MAX)) {

As the first entry in a enum is zero.

Signed-off-by: Yang Jihong <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Clarke <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/Documentation/perf-kwork.txt

@@ -17,8 +17,11 @@ There are several variants of 'perf kwork':
   'perf kwork record <command>' to record the kernel work
   of an arbitrary workload.
 
+  'perf kwork report' to report the per kwork runtime.
+
     Example usage:
         perf kwork record -- sleep 1
+        perf kwork report
 
 OPTIONS
 -------
@@ -38,6 +41,36 @@ OPTIONS
 --verbose::
 	Be more verbose. (show symbol address, etc)
 
+OPTIONS for 'perf kwork report'
+----------------------------
+
+-C::
+--cpu::
+	Only show events for the given CPU(s) (comma separated list).
+
+-i::
+--input::
+	Input file name. (default: perf.data unless stdin is a fifo)
+
+-n::
+--name::
+	Only show events for the given name.
+
+-s::
+--sort::
+	Sort by key(s): runtime, max, count
+
+-S::
+--with-summary::
+	Show summary with statistics
+
+--time::
+	Only analyze samples within given time window: <start>,<stop>. Times
+	have the format seconds.microseconds. If start is not given (i.e., time
+	string is ',x.y') then analysis starts at the beginning of the file. If
+	stop time is not given (i.e, time string is 'x.y,') then analysis goes
+	to end of file.
+
 SEE ALSO
 --------
 linkperf:perf-record[1]