DNS query performance

[Mike Tancsa]

At 01:27 PM 9/13/2006, Robert Watson wrote:

>The other common optimization advice that you may already have 
>received is to check which time counter FreeBSD has selected.  Right 
>now, 6.x/7.x err on the side of accurate over fast.  There's been 
>quite a bit of debate about this approach, and it's useful to 
>investigate the issue.  You can view and set the current choice by 
>looking at the sysctl kern.timecounter.hardware, and you can see the 
>choices on your hardware by looking at kern.timecounter.choice. 
>Typically, TSC is the fastest, but may suffer from drift as the CPU changes


Hi,
         How safe is TSC on SMP systems on RELENG_6 ? Do you still 
have to boot with kern.timecounter.smp_tsc="1" in /boot/loader.conf ? 
I was able to set it to TSC on my SMP box

# sysctl  kern.timecounter
kern.timecounter.tick: 1
kern.timecounter.choice: TSC(-100) ACPI-fast(1000) i8254(0) dummy(-1000000)
kern.timecounter.hardware: TSC
kern.timecounter.nsetclock: 4
kern.timecounter.ngetmicrotime: 1710689523
kern.timecounter.ngetnanotime: 0
kern.timecounter.ngetbintime: 0
kern.timecounter.ngetmicrouptime: 417696361
kern.timecounter.ngetnanouptime: 6622371
kern.timecounter.ngetbinuptime: 17943777
kern.timecounter.nmicrotime: 2454574760
kern.timecounter.nnanotime: 1315721638
kern.timecounter.nbintime: 3770262461
kern.timecounter.nmicrouptime: 407340
kern.timecounter.nnanouptime: 1397760
kern.timecounter.nbinuptime: 3787035688
kern.timecounter.stepwarnings: 0
kern.timecounter.smp_tsc: 0

But the console fills up with

Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379728 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379758 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379789 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379819 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379849 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379879 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379910 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379940 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335379970 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380002 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380032 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380065 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380096 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380126 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380156 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380186 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380216 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380247 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380277 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380307 usec for pid 66442 (clamd)
Sep 13 13:47:57 pumice1 kernel: calcru: runtime went backwards from 
6336196518 usec to 6335380337 usec for pid 66442 (clamd)


So I set things back to
kern.timecounter.hardware: ACPI-fast

         ---Mike