The existing optimizations makes it feasible to have them available on all
builds.

Some quick'n'dirty numbers with 400.perlbench (SPECcpu2006) on the train input
(medium size - suns.pl) and the guest_mem_before event:

* vanilla, statically disabled
real    0m2,259s
user    0m2,252s
sys     0m0,004s

* vanilla, statically enabled (overhead: 2.18x)
real    0m4,921s
user    0m4,912s
sys     0m0,008s

* multi-tb, statically disabled (overhead: 0.99x) [within noise range]
real    0m2,228s
user    0m2,216s
sys     0m0,008s

* multi-tb, statically enabled (overhead: 0.99x) [within noise range]
real    0m2,229s
user    0m2,224s
sys     0m0,004s

Now enabling all events when booting an ARM system that immediately shuts down
(https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg04085.html):

* vanilla, statically disabled
real	0m32,153s
user	0m31,276s
sys	0m0,108s

* vanilla, statically enabled (overhead: 1.35x)
real	0m43,507s
user	0m42,680s
sys	0m0,168s

* multi-tb, statically disabled (overhead: 1.03x)
real	0m32,993s
user	0m32,516s
sys	0m0,104s

* multi-tb, statically enabled (overhead: 1.00x) [within noise range]
real	0m32,110s
user	0m31,176s
sys	0m0,156s

And finally enabling all events using Emilio's dbt-bench
(where orig == vanilla, new == multi-tb):

                                                        NBench score; higher is better

  180 +-+--------+----------+----------+---------+----------+----------+----------+----------+----------+---------+----------+--------+-+
      |                                                                                                                                 |
      |                                      *** $$$$%%                                                                    orig         |
  160 +-+....................................*.*.$..$.%............................................................orig-enabled       +-+
      |                                      * * $  $ %                                                                     new         |
  140 +-+....................................*.*.$..$.%............................................................new-disabled.......+-+
      |                                      * * $  $ %                                                                                 |
      |                                      * * $  $ %                                                                                 |
  120 +-+....................................*.*.$..$.%...............................................................................+-+
      |                                      * * $  $ %                                                                                 |
      |                                      * * $  $ %                                                                                 |
  100 +-+....................................*.*.$..$.%.....$$$%%%....................................................................+-+
      |                                      * * $  $ % *** $ $  % *** $$$%%                                                            |
   80 +-+....................................*.*.$..$.%.*.*.$.$..%.*.*.$.$.%..........................................................+-+
      |                                      * * $  $ % * * $ $  % * * $ $ %                                                            |
      |                                      * * $  $ % * * $ $  % * * $ $ %                                                            |
   60 +-+.........................***..$$$%%.*.*##..$.%.*.*.$.$..%.*.*.$.$.%..***.$$$%%...............................................+-+
      |                **** $$$%% * *  $ $ % * * #  $ % * *## $  % * * $ $ %  * * $ $ %                                                 |
      |                *  * $ $ % * *  $ $ % * * #  $ % * * # $  % * *## $ %  * * $ $ %                                                 |
   40 +-+..............*..*.$.$.%.*.*..$.$.%.*.*.#..$.%.*.*.#.$..%.*.*.#.$.%..*.*.$.$.%...............................................+-+
      |                *  * $ $ % * *  $ $ % * * #  $ % * * # $  % * * # $ %  * *## $ %                                  *** $$$%%%     |
   20 +-+....***.$$$%%.*..*##.$.%.*.*###.$.%.*.*.#..$.%.*.*.#.$..%.*.*.#.$.%..*.*.#.$.%..................................*.*.$.$..%...+-+
      |      * *## $ % *  * # $ % * *  # $ % * * #  $ % * * # $  % * * # $ %  * * # $ %                                  * *## $  %     |
      |      * * # $ % *  * # $ % * *  # $ % * * #  $ % * * # $  % * * # $ %  * * # $ %            ***###$$%% ***##$$$%% * * # $  %     |
    0 +-+----***##$$%%-****##$$%%-***###$$%%-***##$$$%%-***##$$%%%-***##$$%%--***##$$%%-****##$$%%-***###$$%%-***##$$$%%-***##$$%%%---+-+
     NUMERIC SORTSTRING SORT   BITFIEFP EMULATION ASSIGNMENT       IDEA    HUFFMAN    FOURIER NEURLU DECOMPOSITION      gmean
png: http://imgur.com/a/8XG5S



Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-id: 149915849243.6295.4484103824675839071.stgit@frigg.lan
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>