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Diffstat (limited to 'cddl/contrib/dtracetoolkit/Examples/cpuwalk_example.txt')
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diff --git a/cddl/contrib/dtracetoolkit/Examples/cpuwalk_example.txt b/cddl/contrib/dtracetoolkit/Examples/cpuwalk_example.txt new file mode 100644 index 0000000..34afa95 --- /dev/null +++ b/cddl/contrib/dtracetoolkit/Examples/cpuwalk_example.txt @@ -0,0 +1,85 @@ +The following is a demonstration of the cpuwalk.d script, + + +cpuwalk.d is not that useful on a single CPU server, + + # cpuwalk.d + Sampling... Hit Ctrl-C to end. + ^C + + PID: 18843 CMD: bash + + value ------------- Distribution ------------- count + < 0 | 0 + 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 30 + 1 | 0 + + PID: 8079 CMD: mozilla-bin + + value ------------- Distribution ------------- count + < 0 | 0 + 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 10 + 1 | 0 + +The output above shows that PID 18843, "bash", was sampled on CPU 0 a total +of 30 times (we sample at 1000 hz). + + + +The following is a demonstration of running cpuwalk.d with a 5 second +duration. This is on a 4 CPU server running a multithreaded CPU bound +application called "cputhread", + + # cpuwalk.d 5 + Sampling... + + PID: 3 CMD: fsflush + + value ------------- Distribution ------------- count + 1 | 0 + 2 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 30 + 3 | 0 + + PID: 12186 CMD: cputhread + + value ------------- Distribution ------------- count + < 0 | 0 + 0 |@@@@@@@@@@ 4900 + 1 |@@@@@@@@@@ 4900 + 2 |@@@@@@@@@@ 4860 + 3 |@@@@@@@@@@ 4890 + 4 | 0 + +As we are sampling at 1000 hz, the application cputhread is indeed running +concurrently across all available CPUs. We measured the applicaiton on +CPU 0 a total of 4900 times, on CPU 1 a total of 4900 times, etc. As there +are around 5000 samples per CPU available in this 5 second 1000 hz sample, +the application is using almost all the CPU capacity in this server well. + + + +The following is a similar demonstration, this time running a multithreaded +CPU bound application called "cpuserial" that has a poor use of locking +such that the threads "serialise", + + + # cpuwalk.d 5 + Sampling... + + PID: 12194 CMD: cpuserial + + value ------------- Distribution ------------- count + < 0 | 0 + 0 |@@@ 470 + 1 |@@@@@@ 920 + 2 |@@@@@@@@@@@@@@@@@@@@@@@@@ 3840 + 3 |@@@@@@ 850 + 4 | 0 + +In the above, we can see that this CPU bound application is not making +efficient use of the CPU resources available, only reaching 3840 samples +on CPU 2 out of a potential 5000. This problem was caused by a poor use +of locks. + + + |
