1. 08 11月, 2009 1 次提交
    • A
      perf symbols: Use the buildids if present · 8d06367f
      Arnaldo Carvalho de Melo 提交于
      With this change 'perf record' will intercept PERF_RECORD_MMAP
      calls, creating a linked list of DSOs, then when the session
      finishes, it will traverse this list and read the buildids,
      stashing them at the end of the file and will set up a new
      feature bit in the header bitmask.
      
      'perf report' will then notice this feature and populate the
      'dsos' list and set the build ids.
      
      When reading the symtabs it will refuse to load from a file that
      doesn't have the same build id. This improves the
      reliability of the profiler output, as symbols and profiling
      data is more guaranteed to match.
      
      Example:
      
       [root@doppio ~]# perf report | head
       /home/acme/bin/perf with build id b1ea544ac3746e7538972548a09aadecc5753868 not found, continuing without symbols
        # Samples: 2621434559
        #
        # Overhead          Command                  Shared Object  Symbol
        # ........  ...............  .............................  ......
        #
             7.91%             init  [kernel]        [k] read_hpet
             7.64%             init  [kernel]        [k] mwait_idle_with_hints
             7.60%          swapper  [kernel]        [k] read_hpet
             7.60%          swapper  [kernel]        [k] mwait_idle_with_hints
             3.65%             init  [kernel]        [k] 0xffffffffa02339d9
      [root@doppio ~]#
      
      In this case the 'perf' binary was an older one, vanished,
      so its symbols probably wouldn't match or would cause subtly
      different (and misleading) output.
      
      Next patches will support the kernel as well, reading the build
      id notes for it and the modules from /sys.
      
      Another patch should also introduce a new plumbing command:
      
      'perf list-buildids'
      
      that will then be used in porcelain that is distro specific to
      fetch -debuginfo packages where such buildids are present. This
      will in turn allow for one to run 'perf record' in one machine
      and 'perf report' in another.
      
      Future work on having the buildid sent directly from the kernel
      in the PERF_RECORD_MMAP event is needed to close races, as the
      DSO can be changed during a 'perf record' session, but this
      patch at least helps with non-corner cases and current/older
      kernels.
      Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Frank Ch. Eigler <fche@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Jason Baron <jbaron@redhat.com>
      Cc: Jim Keniston <jkenisto@us.ibm.com>
      Cc: K. Prasad <prasad@linux.vnet.ibm.com>
      Cc: Masami Hiramatsu <mhiramat@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Roland McGrath <roland@redhat.com>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      LKML-Reference: <1257367843-26224-1-git-send-email-acme@infradead.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8d06367f
  2. 04 11月, 2009 9 次提交
  3. 03 11月, 2009 30 次提交