perf trace: Add possibility to switch off syscall events

Currently, we may either trace syscalls or syscalls+pagefaults.

We'd like to be able to trace *only* pagefaults and this commit
implements this feature.

Example:

  [root@zoo /]# echo 1 > /proc/sys/vm/drop_caches ; trace --no-syscalls -F -p `pidof xchat`
       0.000 ( 0.000 ms): xchat/4574 majfault [g_unichar_get_script+0x11] => /usr/lib64/libglib-2.0.so.0.3800.2@0xc403b (x.)
       0.202 ( 0.000 ms): xchat/4574 majfault [_cairo_hash_table_lookup+0x53] => 0x2280ff0 (?.)
      20.854 ( 0.000 ms): xchat/4574 majfault [gdk_cairo_set_source_pixbuf+0x110] => /usr/bin/xchat@0x6da1f (x.)
    1022.000 ( 0.000 ms): xchat/4574 majfault [__memcpy_sse2_unaligned+0x29] => 0x7ff5a8ca0400 (?.)
  ^C[root@zoo /]#

Below we can see malloc calls, 'trace' reading symbol tables in libraries to
resolve symbols, etc.

  [root@zoo /]# echo 1 > /proc/sys/vm/drop_caches ; trace --no-syscalls -F all --cpu 1 sleep 10
       0.000 ( 0.000 ms): chrome/26589 minfault [0x1b53129] => /tmp/perf-26589.map@0x33cbcbf7f000 (x.)
      96.477 ( 0.000 ms): libvirtd/947 minfault [copy_user_enhanced_fast_string+0x5] => 0x7f7685bba000 (?k)
     113.164 ( 0.000 ms): Xorg/1063 minfault [0x786da] => 0x7fce52882a3c (?.)
    7162.801 ( 0.000 ms): chrome/3747 minfault [0x8e1a89] => 0xfcaefed0008 (?.)
<SNIP>
    7773.138 ( 0.000 ms): chrome/3886 minfault [0x8e1a89] => 0xfcb0ce28008 (?.)
    7992.022 ( 0.000 ms): chrome/26574 minfault [0x1b5a708] => 0x3de7b5fc5000 (?.)
    8108.949 ( 0.000 ms): qemu-system-x8/4537 majfault [_int_malloc+0xee] => 0x7faffc466d60 (?.)
    8108.975 ( 0.000 ms): qemu-system-x8/4537 minfault [_int_malloc+0x102] => 0x7faffc466d60 (?.)
<SNIP>
    8148.174 ( 0.000 ms): qemu-system-x8/4537 minfault [_int_malloc+0x102] => 0x7faffc4eb500 (?.)
    8270.855 ( 0.000 ms): chrome/26245 minfault [do_bo_emit_reloc+0xdb] => 0x45d092bc004 (?.)
    8270.869 ( 0.000 ms): chrome/26245 minfault [do_bo_emit_reloc+0x108] => 0x45d09150000 (?.)
no symbols found in /usr/lib64/libspice-server.so.1.9.0, maybe install a debug package?
    8273.831 ( 0.000 ms): trace/20198 majfault [__memcmp_sse4_1+0xbc6] => /usr/lib64/libspice-server.so.1.9.0@0xdf000 (d.)
<SNIP>
    8275.121 ( 0.000 ms): trace/20198 minfault [dso__load+0x38] => 0x14fe756 (?.)
no symbols found in /usr/lib64/libelf-0.158.so, maybe install a debug package?
    8275.142 ( 0.000 ms): trace/20198 minfault [__memcmp_sse4_1+0xbc6] => /usr/lib64/libelf-0.158.so@0x0 (d.)
<SNIP>
  [root@zoo /]#

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1403799268-1367-6-git-send-email-stfomichev@yandex-team.ru
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-trace.txt

@@ -112,6 +112,9 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
 	Trace pagefaults. Optionally, you can specify whether you want minor,
 	major or all pagefaults. Default value is maj.
 
+--syscalls::
+	Trace system calls. This options is enabled by default.
+
 PAGEFAULTS
 ----------
 
@@ -137,6 +140,10 @@ for both IP and fault address in the form of dso@symbol+offset.
 EXAMPLES
 --------
 
+Trace only major pagefaults:
+
+ $ perf trace --no-syscalls -F
+
 Trace syscalls, major and minor pagefaults:
 
  $ perf trace -F all