Re: Performance counter's value is 0,why?

Thanks for your reply ,David Long. Can you give me url of the kernel version 3.4.19?Thanks.

2012/12/5 David Long dave.long@linaro.org

On 12/04/12 13:46, Scott Bambrough wrote:

...

• Dave Long

On Tue, Dec 4, 2012 at 3:37 AM, Peng Fan <xfan87@gmail.com mailto: xfan87@gmail.com> wrote:

I use the option `-v`, and I can see that the first number of
branches, instructions branch-misses and so on is zero.why?

root@android:/ # perf stat -v echo "linaro"
linaro
task-clock: 93902590 93902590 93902590

context-switches: 9 93902590 93902590

CPU-migrations: 0 93902590 93902590
page-faults: 104 93902590 93902590
cycles: 4284725 76202392 76202392
stalled-cycles-frontend: 0 76202392 76202392
stalled-cycles-backend: 0 76202392 76202392
instructions: 0 76202392 76202392
branches: 0 76202392 76202392
branch-misses: 0 76202392 76202392

 Performance counter stats for 'echo linaro':

         93.902590 task-clock                #    0.282 CPUs utilized
                 9 context-switches          #    0.000 M/sec
                 0 CPU-migrations            #    0.000 M/sec
               104 page-faults               #    0.001 M/sec
           4284725 cycles                    #    0.046 GHz
*                 0 stalled-cycles-frontend   #    0.00% frontend

cycles idle
                 0 stalled-cycles-backend    #    0.00% backend

cycles idle 0 instructions # 0.00 insns per cycle 0 branches # 0.000 M/sec 0 branch-misses # 0.00% of all branches *

       0.332550049 seconds time elapsed

Can anybody give me suggestions?How can I use perf to get the
value of hardware performance counter

Using a recent 3.4.19 kernel I am unable to reproduce your results:

context-switches: 0 8941650 8941650 CPU-migrations: 0 8941650 8941650 page-faults: 147 8941650 8941650 cycles: 2665204 8941650 8941650 stalled-cycles-frontend: 365973 8941650 8941650 stalled-cycles-backend: 1748465 8941650 8941650 instructions: 1368842 8941650 8941650 branches: 152838 8941650 8941650 branch-misses: 53924 8941650 8941650

Performance counter stats for 'echo linaro':

      8.941650 task-clock                #    0.740 CPUs utilized
             0 context-switches          #    0.000 K/sec
             0 CPU-migrations            #    0.000 K/sec
           147 page-faults               #    0.016 M/sec
       2665204 cycles                    #    0.298 GHz
        365973 stalled-cycles-frontend   #   13.73% frontend cycles

idle 1748465 stalled-cycles-backend # 65.60% backend cycles idle 1368842 instructions # 0.51 insns per cycle # 1.28 stalled cycles per insn 152838 branches # 17.093 M/sec 53924 branch-misses # 35.28% of all branches

   0.012084973 seconds time elapsed

Significant changes were made the the counter/event kernel code about the time of the release. I do not believe they made it in in time. Please try simply using a slightly more recent kernel.

-- David Long Kernel Engineer, TI Landing Team Linaro