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