perf lock contention: Constify control data for BPF

The control knobs set before loading BPF programs should be declared as
'const volatile' so that it can be optimized by the BPF core.

Committer testing:

  root@x1:~# perf lock contention --use-bpf
   contended   total wait     max wait     avg wait         type   caller

           5     31.57 us     14.93 us      6.31 us        mutex   btrfs_delayed_update_inode+0x43
           1     16.91 us     16.91 us     16.91 us      rwsem:R   btrfs_tree_read_lock_nested+0x1b
           1     15.13 us     15.13 us     15.13 us     spinlock   btrfs_getattr+0xd1
           1      6.65 us      6.65 us      6.65 us      rwsem:R   btrfs_tree_read_lock_nested+0x1b
           1      4.34 us      4.34 us      4.34 us     spinlock   process_one_work+0x1a9
  root@x1:~#
  root@x1:~# perf trace -e bpf --max-events 10 perf lock contention --use-bpf
       0.000 ( 0.013 ms): :2948281/2948281 bpf(cmd: 36, uattr: 0x7ffd5f12d730, size: 8)          = -1 EOPNOTSUPP (Operation not supported)
       0.024 ( 0.120 ms): :2948281/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d460, size: 148) = 16
       0.158 ( 0.034 ms): :2948281/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d520, size: 148) = 16
      26.653 ( 0.154 ms): perf/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d3d0, size: 148)     = 16
      26.825 ( 0.014 ms): perf/2948281 bpf(uattr: 0x7ffd5f12d580, size: 80)                      = 16
      87.924 ( 0.038 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d400, size: 40)       = 16
      87.988 ( 0.006 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d470, size: 40)       = 16
      88.019 ( 0.006 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d250, size: 40)       = 16
      88.029 ( 0.172 ms): perf/2948281 bpf(cmd: PROG_LOAD, uattr: 0x7ffd5f12d320, size: 148)     = 17
      88.217 ( 0.005 ms): perf/2948281 bpf(cmd: BTF_LOAD, uattr: 0x7ffd5f12d4d0, size: 40)       = 16
  root@x1:~#

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240902200515.2103769-5-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>