Enable option TCPHPTS in the kernel causes a large % of interruptions if there is no HPET eventtimer in the system.

FreeBSD system running on VPS with 1 GB of RAM in the OVH data center

# uname -a
FreeBSD vps7XXXXX.ovh.net 12.1-STABLE FreeBSD 12.1-STABLE r354671 SUPPORT-12-1-3  amd64

#top -CHPS
last pid: 54135;  load averages:  1.13,  0.83,  0.83    up 0+00:40:41  01:17:27
370 threads:   2 running, 342 sleeping, 26 waiting
CPU:  0.0% user,  0.0% nice,  0.4% system, 41.6% interrupt, 58.0% idle
Mem: 87M Active, 23M Inact, 118M Wired, 1677M Free
ARC: 40M Total, 5499K MFU, 32M MRU, 1220K Anon, 395K Header, 1405K Other
     21M Compressed, 61M Uncompressed, 2.97:1 Ratio
Swap: 1024M Total, 1024M Free

  PID USERNAME    PRI NICE   SIZE    RES STATE    TIME     CPU COMMAND
   11 root        155 ki31      0    16K RUN     27:09  57.51% idle
   12 root        -72    -      0   416K WAIT    13:12  42.04% intr{swi1: hpts}

# sysctl -a kern.eventtimer
kern.eventtimer.periodic: 0
kern.eventtimer.timer: LAPIC
kern.eventtimer.idletick: 0
kern.eventtimer.singlemul: 4
kern.eventtimer.choice: LAPIC(600) i8254(100) RTC(0)
kern.eventtimer.et.i8254.quality: 100
kern.eventtimer.et.i8254.frequency: 1193182
kern.eventtimer.et.i8254.flags: 1
kern.eventtimer.et.RTC.quality: 0
kern.eventtimer.et.RTC.frequency: 32768
kern.eventtimer.et.RTC.flags: 17
kern.eventtimer.et.LAPIC.quality: 600
kern.eventtimer.et.LAPIC.frequency: 500011170
kern.eventtimer.et.LAPIC.flags: 7

# sysctl -a net.inet.tcp.hpts
net.inet.tcp.hpts.0.logsize: 3072
net.inet.tcp.hpts.0.curtick: 284411163
net.inet.tcp.hpts.0.curslot: 46360
net.inet.tcp.hpts.0.active: 0
net.inet.tcp.hpts.0.out_qcnt: 0
net.inet.tcp.hpts.0.in_qcnt: 0
net.inet.tcp.hpts.log:
net.inet.tcp.hpts.skip_swi: 0
net.inet.tcp.hpts.minsleep: 250
net.inet.tcp.hpts.maxsleep: 102398
net.inet.tcp.hpts.out_tspercision: 0
net.inet.tcp.hpts.out_tsperpcb: 0
net.inet.tcp.hpts.in_tspercision: 0
net.inet.tcp.hpts.in_tsperpcb: 0
net.inet.tcp.hpts.no_tcbsfound: 0
net.inet.tcp.hpts.loops: 42998907
net.inet.tcp.hpts.logging: 0
net.inet.tcp.hpts.precision: 120



#dmesg
FreeBSD 12.1-STABLE r354671 SUPPORT-12-1-0 amd64
FreeBSD clang version 8.0.1 (tags/RELEASE_801/final 366581) (based on LLVM 8.0.1)
sysctl: OID number(131) is already in use for 'me'
VT(vga): resolution 640x480
CPU: Intel Core Processor (Haswell, no TSX) (2400.01-MHz K8-class CPU)
  Origin="GenuineIntel"  Id=0x306c1  Family=0x6  Model=0x3c  Stepping=1
  Features=0x783fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR,SSE,SSE2>
  Features2=0xfffa3223<SSE3,PCLMULQDQ,VMX,SSSE3,FMA,CX16,PCID,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND,HV>
  AMD Features=0x28100800<SYSCALL,NX,RDTSCP,LM>
  AMD Features2=0x21<LAHF,ABM>
  Structured Extended Features=0x7a9<FSGSBASE,BMI1,AVX2,SMEP,BMI2,ERMS,INVPCID>
  XSAVE Features=0x1<XSAVEOPT>
  VT-x: (disabled in BIOS) PAT,HLT,MTF,PAUSE,EPT,UG,VPID,VID,PostIntr
Hypervisor: Origin = "KVMKVMKVM"
...