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    • Peter Zijlstra's avatar
      perf, x86: Update/fix Intel Nehalem cache events · f4929bd3
      Peter Zijlstra authored
      
      
      Change the Nehalem cache events to use retired memory instruction counters
      (similar to Westmere), this greatly improves the provided stats.
      
      Using:
      
      main ()
      {
              int i;
      
              for (i = 0; i < 1000000000; i++) {
                      asm("mov (%%rsp), %%rbx;"
                          "mov %%rbx, (%%rsp);" : : : "rbx");
              }
      }
      
      We find:
      
       $ perf stat --repeat 10 -e instructions:u -e l1-dcache-loads:u -e l1-dcache-stores:u ./loop_1b_loads+stores
        Performance counter stats for './loop_1b_loads+stores' (10 runs):
            4,000,081,056 instructions:u           #      0.000 IPC ( +-   0.000% )
            4,999,502,846 l1-dcache-loads:u          ( +-   0.008% )
            1,000,034,832 l1-dcache-stores:u         ( +-   0.000% )
               1.565184942  seconds time elapsed   ( +-   0.005% )
      
      The 5b is surprising - we'd expect 1b:
      
       $ perf stat --repeat 10 -e instructions:u -e r10b:u -e l1-dcache-stores:u ./loop_1b_loads+stores
        Performance counter stats for './loop_1b_loads+stores' (10 runs):
            4,000,081,054 instructions:u           #      0.000 IPC ( +-   0.000% )
            1,000,021,961 r10b:u                     ( +-   0.000% )
            1,000,030,951 l1-dcache-stores:u         ( +-   0.000% )
               1.565055422  seconds time elapsed   ( +-   0.003% )
      
      Which this patch thus fixes.
      
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Stephane Eranian <eranian@google.com>
      Cc: Lin Ming <ming.m.lin@intel.com>
      Cc: Cyrill Gorcunov <gorcunov@openvz.org>
      Link: http://lkml.kernel.org/n/tip-q9rtru7b7840tws75xzboapv@git.kernel.org
      
      
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      f4929bd3