• Jin Yao's avatar
    perf stat: Ignore error thread when enabling system-wide --per-thread · ab6c79b8
    Jin Yao authored
    If we execute 'perf stat --per-thread' with non-root account (even set
    kernel.perf_event_paranoid = -1 yet), it reports the error:
    
      jinyao@skl:~$ perf stat --per-thread
      Error:
      You may not have permission to collect system-wide stats.
    
      Consider tweaking /proc/sys/kernel/perf_event_paranoid,
      which controls use of the performance events system by
      unprivileged users (without CAP_SYS_ADMIN).
    
      The current value is 2:
    
        -1: Allow use of (almost) all events by all users
            Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
      >= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
            Disallow raw tracepoint access by users without CAP_SYS_ADMIN
      >= 1: Disallow CPU event access by users without CAP_SYS_ADMIN
      >= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN
    
      To make this setting permanent, edit /etc/sysctl.conf too, e.g.:
    
              kernel.perf_event_paranoid = -1
    
    Perhaps the ptrace rule doesn't allow to trace some processes. But anyway
    the global --per-thread mode had better ignore such errors and continue
    working on other threads.
    
    This patch will record the index of error thread in perf_evsel__open()
    and remove this thread before retrying.
    
    For example (run with non-root, kernel.perf_event_paranoid isn't set):
    
      jinyao@skl:~$ perf stat --per-thread
      ^C
       Performance counter stats for 'system wide':
    
             vmstat-3458    6.171984   cpu-clock:u (msec) #  0.000 CPUs utilized
               perf-3670    0.515599   cpu-clock:u (msec) #  0.000 CPUs utilized
             vmstat-3458   1,163,643   cycles:u           #  0.189 GHz
               perf-3670      40,881   cycles:u           #  0.079 GHz
             vmstat-3458   1,410,238   instructions:u     #  1.21  insn per cycle
               perf-3670       3,536   instructions:u     #  0.09  insn per cycle
             vmstat-3458     288,937   branches:u         # 46.814 M/sec
               perf-3670         936   branches:u         #  1.815 M/sec
             vmstat-3458      15,195   branch-misses:u    #  5.26% of all branches
               perf-3670          76   branch-misses:u    #  8.12% of all branches
    
            12.651675247 seconds time elapsed
    Signed-off-by: default avatarJin Yao <yao.jin@linux.intel.com>
    Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
    Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Kan Liang <kan.liang@intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lkml.kernel.org/r/1516117388-10120-1-git-send-email-yao.jin@linux.intel.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    ab6c79b8
evsel.c 70.7 KB