As it was not being exposed via any command line and with --dsos/--comms
we can do this and even more, like asking for just kernel + some module:

[root@doppio linux-2.6-tip]# perf report --dsos \[kernel\],\[drm\]
--vmlinux /home/acme/git/build/tip-recvmmsg/vmlinux --modules | head -15
 # Samples: 619669
 #
 # Overhead          Command  Shared Object  Symbol
 # ........  ...............  .............  ......
 #
      7.12%          swapper  [kernel]       [k] read_hpet
      6.86%             init  [kernel]       [k] read_hpet
      6.22%             init  [kernel]       [k] mwait_idle_with_hints
      5.34%          swapper  [kernel]       [k] mwait_idle_with_hints
      3.01%          firefox  [kernel]       [.] vread_hpet
      2.14%             Xorg  [drm]          [k] drm_clflush_pages
      2.09%           pidgin  [kernel]       [.] vread_hpet
      1.58%     npviewer.bin  [kernel]       [.] vread_hpet
      1.37%          swapper  [kernel]       [k] hpet_next_event
      1.23%             Xorg  [kernel]       [k] read_hpet
[root@doppio linux-2.6-tip]#
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091003233048.GA30535@ghostprotocols.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>