title: perf have no permission to collect stats
body: <p>When I use perf to collect system stats, like this</p>
  
  <pre><code>sudo perf record -a -g -F 997 -p pid sleep 30
  </code></pre>
  
  <p>then I got</p>
  
  <pre><code>Error:
  You may not have permission to collect stats.
  Consider tweaking /proc/sys/kernel/perf_event_paranoid:
   -1 - Not paranoid at all
    0 - Disallow raw tracepoint access for unpriv
    1 - Disallow cpu events for unpriv
    2 - Disallow kernel profiling for unpriv
  </code></pre>
  
  <p>I have no permission to modify <code>/proc/sys/kernel/perf_event_paranoid</code>, even in <code>root</code>.
  I try to add <code>"kernal.perf_event_paranoid=-1"</code> into <code>/etc/sysctl.conf</code>, and use</p>
  
  <pre><code>sysctl -p
  </code></pre>
  
  <p>to reload params.
  Again I have no permission to load param kernal.perf_event_paranoid.</p>
  
  <p>How can I use perf to collect stats?</p>