perf_counter tools: include PID in perf-report output, tweak user/kernel printut

It's handier than an <unknown> entry.
Also replace the kernel/user column with a more compact version:

  0.52              cc1  [k]  page_fault
  0.57               :0  [k]   _spin_lock
  0.59            :7506  [.]  <unknown>
  0.69               as  [.]  /usr/bin/as: <unknown>
  0.76              cc1  [.]  /lib64/libc-2.8.so: _int_free
  0.92              cc1  [k]  clear_page_c
  1.00            :7465  [.]  <unknown>
  1.43              cc1  [.]  /lib64/libc-2.8.so: memset
  1.86              cc1  [.]  /lib64/libc-2.8.so: _int_malloc
 70.33              cc1  [.]  /usr/libexec/gcc/x86_64-redhat-linux/4.3.2/cc1: <unknown>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Documentation/perf_counter/perf-report.cc

@@ -277,10 +277,17 @@ static std::multimap<int, std::string> rev_hist;
 
 static std::string resolve_comm(int pid)
 {
-	std::string comm = "<unknown>";
+	std::string comm;
+
 	std::map<int, std::string>::const_iterator ci = comms.find(pid);
-	if (ci != comms.end())
+	if (ci != comms.end()) {
 		comm = ci->second;
+	} else {
+		char pid_str[30];
+
+		sprintf(pid_str, ":%d", pid);
+		comm = pid_str;
+	}
 
 	return comm;
 }
@@ -422,13 +429,13 @@ more:
 		char output[1024];
 
 		if (event->header.misc & PERF_EVENT_MISC_KERNEL) {
-			level = "[kernel]";
+			level = " [k] ";
 			sym = resolve_kernel_symbol(event->ip.ip);
 		} else if (event->header.misc & PERF_EVENT_MISC_USER) {
-			level = "[ user ]";
+			level = " [.] ";
 			sym = resolve_user_symbol(event->ip.pid, event->ip.ip);
 		} else {
-			level = "[  hv  ]";
+			level = " [H] ";
 		}
 		comm = resolve_comm(event->ip.pid);