fix(inputs.intel_powerstat): reduce msr read latency on preempt-rt kernels

[alysondeives]

fixes: #13828

Using cyclictest utility from rt-tests [1] results on latency increase when telegraf is executed on a preempt-rt kernel. This increase occurs because of the concurrent read of MSR with goroutines.

To fix this issue, the MSR read was changed to be sequential.

[1] https://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git

[telegraf-tiger]

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DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[p-zak]

I described background for concurrent reading in #13828, here is summary:

I'm ok with reading MSRs sequentially as long as:

• it will depend on config parameter, for example: read_method with possible values: concurrent or sequential
• default will be: concurrent (to have calculations as precise as possible by default and also for backward compatibility)
• it will be very well described in README.md, sample.conf and code to show user pros and cons of each option
  • please search for all occurrences of read_method in https://github.com/influxdata/telegraf/blob/master/plugins/inputs/smart/README.md to see how it can be done

[alysondeives]

HI @p-zak thanks for the explanation on MSR reads.
I will follow your recommendations and update my pull request.

[telegraf-tiger]

Hello! I am closing this issue due to inactivity. I hope you were able to resolve your problem, if not please try posting this question in our Community Slack or Community Forums or provide additional details in this issue and reqeust that it be re-opened. Thank you!