Debian Stretch 2.7-rtpreempt latency issues.

latheoperator@125cnc:~$ ps -ef | grep laten
latheop+  4154  3348  0 17:18 pts/0    00:00:00 /bin/bash /usr/bin/latency-test 1000000 1000000
latheop+  4442  3489  0 17:18 pts/1    00:00:00 grep laten
latheoperator@125cnc:~$ chrt -p 4154
pid 4154's current scheduling policy: SCHED_OTHER
pid 4154's current scheduling priority: 0
latheoperator@125cnc:~$ pstree 4154
latency-test───halrun───halcmd─┬─pyvcp───{pyvcp}
                               └─rtapi_app───{rtapi_app}
latheoperator@125cnc:~$ ps -ef | grep rtapi
root      4180  4179  0 17:18 ?        00:00:00 /usr/bin/rtapi_app load threads name1=slow period1=1000000
latheop+  4630  3489  0 17:19 pts/1    00:00:00 grep rtapi
latheoperator@125cnc:~$ chrt -p 4180
pid 4180's current scheduling policy: SCHED_OTHER
pid 4180's current scheduling priority: 0
latheoperator@125cnc:~$ ls -l /usr/bin/rtapi_app 
-rwsr-xr-x 1 root root 102224 Nov 19 15:38 /usr/bin/rtapi_app
latheoperator@125cnc:~$ uname -a
Linux 125cnc 4.8.0-1-rt-amd64 #1 SMP PREEMPT RT Debian 4.8.5-1 (2016-10-28) x86_64 GNU/Linux

root@125cnc:~# cat /proc/cpuinfo 
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 78
model name	: Intel(R) Celeron(R) CPU 3855U @ 1.60GHz
stepping	: 3
microcode	: 0x9e
cpu MHz		: 1600.000
cache size	: 2048 KB
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 22
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave rdrand lahf_lm abm 3dnowprefetch epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust erms invpcid rdseed smap clflushopt xsaveopt xsavec xgetbv1 xsaves dtherm arat pln pts hwp hwp_notify hwp_act_window hwp_epp
bugs		:
bogomips	: 3216.00
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 78
model name	: Intel(R) Celeron(R) CPU 3855U @ 1.60GHz
stepping	: 3
microcode	: 0x9e
cpu MHz		: 1600.000
cache size	: 2048 KB
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 2
initial apicid	: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 22
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave rdrand lahf_lm abm 3dnowprefetch epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust erms invpcid rdseed smap clflushopt xsaveopt xsavec xgetbv1 xsaves dtherm arat pln pts hwp hwp_notify hwp_act_window hwp_epp
bugs		:
bogomips	: 3217.14
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

root@125cnc:~# free
              total        used        free      shared  buff/cache   available
Mem:        3928112      634176     2112840      109388     1181096     3118296
Swap:       6369276           0     6369276
root@125cnc:~# lspci
00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 510 (rev 07)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI (rev 21)
00:17.0 SATA controller: Intel Corporation Sunrise Point-LP SATA Controller [AHCI mode] (rev 21)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point-LP LPC Controller (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-LM (rev 21)
01:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8821AE 802.11ac PCIe Wireless Network Adapter

latheoperator@125cnc:~$ pstree 4154
latency-test───halrun───halcmd─┬─pyvcp───{pyvcp}
                               └─rtapi_app───{rtapi_app}
latheoperator@125cnc:~$ ps -ef | grep rtapi
root      4180  4179  0 17:18 ?        00:00:00 /usr/bin/rtapi_app load threads name1=slow period1=1000000
latheop+  4630  3489  0 17:19 pts/1    00:00:00 grep rtapi
latheoperator@125cnc:~$ chrt -p 4180
pid 4180's current scheduling policy: SCHED_OTHER
pid 4180's current scheduling priority: 0