tools/perf/arch/x86/util/topdown.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <stdio.h>
   3 #include "api/fs/fs.h"
   4 #include "util/pmu.h"
   5 #include "util/topdown.h"
   6
   7 /*
   8  * Check whether we can use a group for top down.
   9  * Without a group may get bad results due to multiplexing.
  10  */
  11 bool arch_topdown_check_group(bool *warn)
  12 {
  13         int n;
  14
  15         if (sysctl__read_int("kernel/nmi_watchdog", &n) < 0)
  16                 return false;
  17         if (n > 0) {
  18                 *warn = true;
  19                 return false;
  20         }
  21         return true;
  22 }
  23
  24 void arch_topdown_group_warn(void)
  25 {
  26         fprintf(stderr,
  27                 "nmi_watchdog enabled with topdown. May give wrong results.\n"
  28                 "Disable with echo 0 > /proc/sys/kernel/nmi_watchdog\n");
  29 }
  30
  31 #define TOPDOWN_SLOTS           0x0400
  32
  33 static bool is_topdown_slots_event(struct evsel *counter)
  34 {
  35         if (!counter->pmu_name)
  36                 return false;
  37
  38         if (strcmp(counter->pmu_name, "cpu"))
  39                 return false;
  40
  41         if (counter->core.attr.config == TOPDOWN_SLOTS)
  42                 return true;
  43
  44         return false;
  45 }
  46
  47 /*
  48  * Check whether a topdown group supports sample-read.
  49  *
  50  * Only Topdown metic supports sample-read. The slots
  51  * event must be the leader of the topdown group.
  52  */
  53
  54 bool arch_topdown_sample_read(struct evsel *leader)
  55 {
  56         if (!pmu_have_event("cpu", "slots"))
  57                 return false;
  58
  59         if (is_topdown_slots_event(leader))
  60                 return true;
  61
  62         return false;
  63 }