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Date: Mon, 27 Aug 2001 10:36:47 -0700 (PDT)
From: Blapp Martin <mb@imp.ch>
To: freebsd-gnats-submit@FreeBSD.org
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Subject: kern/30135: Time drifting on STABLE SMP when calling gettimeofday().
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>Number:         30135
>Category:       kern
>Synopsis:       Time drifting on STABLE SMP when calling gettimeofday().
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Aug 27 10:40:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Blapp Martin
>Release:        4.4-PRERELEASE
>Organization:
Improware AG
>Environment:
FreeBSD xx.xx.xx 4.4-PRERELEASE FreeBSD 4.4-PRERELEASE #1:
Thu Aug 16 15:17:53 CEST 2001
root@xx:/usr/obj/usr/src/sys/DOCSIS  i386
>Description:
Serverworks Chipset

Timecounter "i8254"  frequency 1193182 Hz
CPU: Pentium III/Pentium III Xeon/Celeron (933.37-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0x686  Stepping = 6
  Features=0x383fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR,SSE>

Changing APIC ID for IO APIC #1 from 3 to 1 in MP table
Changing APIC ID for IO APIC #1 from 3 to 1 on chip
Programming 16 pins in IOAPIC #0
IOAPIC #0 intpin 2 -> irq 0
Programming 16 pins in IOAPIC #1
FreeBSD/SMP: Multiprocessor motherboard
 cpu0 (BSP): apic id:  3, version: 0x00040011, at 0xfee00000
 cpu1 (AP):  apic id:  0, version: 0x00040011, at 0xfee00000
 io0 (APIC): apic id:  2, version: 0x000f0011, at 0xfec00000
 io1 (APIC): apic id:  1, version: 0x000f0011, at 0xfec01000
>How-To-Repeat:
If you produce 100% load with this program on one CPU, the time drifting
happens. The drift is about 10% !!!

It seems that gettimeofday() produces the effect. Other load
does not make anything and seems to be harmless.

#include <sys/types.h>
#include <sys/time.h>
#include <err.h>

int
main(void)
{
	
	for(;;) {
		struct timeval tv;
		struct timezone tz;
		gettimeofday(&tv, &tz);
	}
	return (0);
}
>Fix:
Not known.

This is really a severe Problem on bigger servers ! Ntpd gives up after
some minutes cause the jitter is to big, and calling ntpdate all 10 seconds
is not really a solution.
>Release-Note:
>Audit-Trail:
>Unformatted:

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