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switch on schedstat support via sysctl on newer kernel #12

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mbiebl opened this issue Jul 20, 2016 · 3 comments
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switch on schedstat support via sysctl on newer kernel #12

mbiebl opened this issue Jul 20, 2016 · 3 comments
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enhancement

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@mbiebl
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mbiebl commented Jul 20, 2016

As of kernel 4.6, there is now a run-time switch for schedstats support, which defaults to disabled.
It can be switched on via a kernel command line parameter or sysctl [1]

Please update systemd-bootchart to automatically flip that runtime switch via sysctl so fiddling with the kernel command line is not necessary.

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=cb2517653fccaf9f9b4ae968c7ee005c1bbacd
@sofar
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sofar commented Jul 26, 2016

Good catch.

I think we can just write 1 to /proc/sys/kernel/sched_schedstats and ignore any errors. If the file is missing it's likely an older kernel, or the feature is disabled.

We may just want to leave a note in the bootchart.svg that schedstats are possibly disabled.

@sofar sofar mentioned this issue Aug 30, 2016
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@sofar sofar closed this as completed in #16 Sep 14, 2016
sofar added a commit that referenced this issue Sep 14, 2016
@sofar
Switch on schedstat support where needed. (#16)
997273a 
Newer kernels have schedstat disabled by default unless turned on
at runtime or through a kernel parameter/syscall. We should turn
this on irregardless if we can.

If the kernel is too old, any errors in this code will be ignored
as schedstat should be enabled already.

Fixes #12.
sofar added a commit that referenced this issue Sep 14, 2016
@sofar @ahkok
Switch on schedstat support where needed. (#16)
cc00b71 
Newer kernels have schedstat disabled by default unless turned on
at runtime or through a kernel parameter/syscall. We should turn
this on irregardless if we can.

If the kernel is too old, any errors in this code will be ignored
as schedstat should be enabled already.

Fixes #12.
@mbiebl
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mbiebl commented Sep 14, 2016

Yep, works nicely now (on Debian unstable with kernel 4.7.0-1-amd64)

@sofar
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sofar commented Sep 14, 2016

Awesome, thanks for confirming.

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