latency-histogram gets error messages

Yow! 16 ms is not good. I suspect you built a non-realtime kernel:
# CONFIG_PREEMPT_RT_FULL is not set

If you use xconfig, the preemption options are in the processor types and features section
and you need to select the "fully preemptable kernel" option

16017587 servo thread (1ms)

not good.

This indicates something wrong as well: 1) did you ./configure --with-realtime=uspace ?
2) did you make setuid ?

I wonder if there are items not tagged with
CONFIG_PREEMPT that are important for the kernel
build. You may need to find a working preempt-rt
kernel config file for your kernel version.

---

I notice on my (older, debian jessie) working uspace
config has items not listed as set in your grep output:
CONFIG_PREEMPT_RT_BASE=y
CONFIG_PREEMPT_LAZY=y
CONFIG_PREEMPT_RT_FULL=y
CONFIG_DEBUG_PREEMPT=y

and some that are not set (where you have it set):
# CONFIG_PREEMPT__LL is not set


Ref:

Can you post your config file?
Thanks,
Steve

added .txt suffix for forum acceptance

I re-built and get the following for jitter:
7,825,205 servo thread (1ms)
7,931,188 base thread (25us)
which is about 1/2 of what it was before.
I checked for PREEMPT in .config:
CONFIG_PREEMPT_RCU=y
CONFIG_PREEMPT_NOTIFIERS=y
CONFIG_PREEMPT=y
CONFIG_PREEMPT_RT_BASE=y
CONFIG_HAVE_PREEMPT_LAZY=y
CONFIG_PREEMPT_LAZY=y
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT__LL is not set
# CONFIG_PREEMPT_RTB is not set
CONFIG_PREEMPT_RT_FULL=y
CONFIG_PREEMPT_COUNT=y
# CONFIG_DEBUG_PREEMPT is not set
# CONFIG_PREEMPT_TRACER is not set

But then I noticed that ACPI was still enabled. I wasn't able to disable ACPI using "make gconfig", either as me or as root, so I edited .config manually, and re-built...
and CONFIG_ACPI is changed back to "y" when I run "make"! WTF?

8 ms is still quite terrible, there's very likely some basic setup still wrong

Do you have all power management disabled in the BIOS setup? (including all Cstates)

Here's a third gen I5 running Preempt-RT:

freeby.mesanet.com/elite8300-preempt-rt.png

(The Latency problem is not too likely to be ACPI related plus you need some ACPI functions for power down etc)