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runtime/pprof: TestCPUProfileMultithreaded is flaky on ppc64le #13223

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mwhudson opened this issue Nov 13, 2015 · 7 comments
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runtime/pprof: TestCPUProfileMultithreaded is flaky on ppc64le #13223

mwhudson opened this issue Nov 13, 2015 · 7 comments
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@mwhudson
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For example from http://build.golang.org/log/a58e91460d1b6bec7380bd3f9f86f57483aa2e22:

--- FAIL: TestCPUProfileMultithreaded (0.25s)
    pprof_test.go:165: total 12 CPU profile samples collected
    pprof_test.go:181: runtime/pprof_test.cpuHog1: 0
    pprof_test.go:181: runtime/pprof_test.cpuHog2: 12
    pprof_test.go:195: runtime/pprof_test.cpuHog1 has 0 samples out of 12, want at least 1, ideally 6
FAIL

Very old neurons recall that the timer on powerpc has pretty low resolution, but I don't know if that is true or the problem here.
@rsc rsc added this to the Go1.6Maybe milestone Dec 28, 2015
@aclements
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@davecheney, can you provide the kernel config for the linux-ppc64le-canonical builder? In particular, if CONFIG_HIGH_RES_TIMERS is not set, this is probably the same as #13405.

@aclements
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I'm guessing it's this one: http://kernel.ubuntu.com/~kernel-ppa/configs/trusty/ppc64el-config.flavour.generic, which does have CONFIG_HIGH_RES_TIMERS set.

@rsc
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rsc commented Jan 6, 2016

@aclements, what's the magic /proc file to look in to find out timer resolution?

@aclements
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grep resolution: /proc/timer_list

@rsc
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rsc commented Jan 6, 2016 via email

@davecheney
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@rsc from the canonical ppc64le machine

winton-01(~) % grep resolution: /proc/timer_list
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs
  .resolution: 1 nsecs

@gopherbot
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CL https://golang.org/cl/18683 mentions this issue.

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