Messages in this thread |  | | | Subject | Re: Test program for counters in groups | | From | Peter Zijlstra <> | | Date | Thu, 19 Mar 2009 18:41:35 +0100 |
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On Wed, 2009-03-18 at 10:27 +1100, Paul Mackerras wrote: > Here's a little test program that checks whether software counters > (specifically, the task clock counter) work correctly when they're in > a group with hardware counters. > > What it does is to create several groups, each with one hardware > counter, counting instructions, plus a task clock counter. It needs > to know an upper bound N on the number of hardware counters you have > (N defaults to 8), and it creates N+4 groups to force them to be > multiplexed. It also creates an overall task clock counter. > > Then it spins for a while, and then stops all the counters and reads > them. It takes the total of the task clock counters in the groups and > computes the ratio of that total to the overall execution time from > the overall task clock counter. > > That ratio should be equal to the number of actual hardware counters > that can count instructions. If the task clock counters in the groups > don't stop when their group gets taken off the PMU, the ratio will > instead be close to N+4. The program will declare that the test fails > if the ratio is greater than N (actually, N + 0.0001 to allow for FP > rounding errors). > > Could someone run this on x86 on the latest PCL tree and let me know > what happens? I don't have an x86 crash box easily to hand. On > powerpc, it passes, but I think that is because I am missing setting > counter->prev_count in arch/powerpc/kernel/perf_counter.c, and I think > that means that enabling/disabling a group with a task clock counter > in it won't work correctly (I'll do a test program for that next). > > Usage is: swsched-test [-c num-hw-counters] [-v] > > Use -c N if you have more than 8 hardware counters. The -v flag makes > it print out the values of each counter.
Adapted the thing a little for the latest ABI, but it seems to work:
[root@opteron ~]# ./swsched-test overall task clock: 3211403572 hw sum: 12150279972, task clock sum: 12845614288 ratio: 4.00 test passed
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