Date: Sat, 5 Sep 1998 08:14:15 -0700 (PDT) From: Thomas Dean <tomdean@ix.netcom.com> To: current@FreeBSD.ORG Subject: Dmesg Timecounter Varies Message-ID: <199809051514.IAA00899@ix.netcom.com>
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I have noticed that the Timecounter value varies greatly in DMESG.
I am running an SMP kernel. I extracted the values from
/var/log/messages and passed them thru a stat process:
Timecounter Cost Statistics
Processing /var/log/messages and /var/log/messages.?.gz
Frequency: 1193182 Hz - Always this value, unless stated.
1/freq Time: 838 nsec
No. Cycles: 3 - floor( mean/(1/freqTime) ).
Cycle Time: 948 nsec - mean/(no. cycles).
Overhead: 332 nsec - Total overhead in Timecounter cost.
Entries: 125 - Number of Timecounter entries in messages.
Minimum: 2517 nsec
Maximum: 41603 nsec - Wow! Flyer!
Mean: 2846 nsec
Std. Dev.: 3494.46
Notice the maximum flyer. What causes this variability?
============= dmesg ==================================
FreeBSD 3.0-CURRENT #2: Tue Aug 18 14:05:12 PDT 1998
root@celebris:/usr/src/sys/compile/CELEBRIS-SMP
Timecounter "i8254" frequency 1193182 Hz cost 2540 ns
CPU: Pentium/P54C (586-class CPU)
Origin = "GenuineIntel" Id = 0x525 Stepping=5
Features=0x3bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,APIC>
real memory = 100663296 (98304K bytes)
avail memory = 95268864 (93036K bytes)
FreeBSD/SMP: Multiprocessor motherboard
cpu0 (BSP): apic id: 0, version: 0x00030010, at 0xfee00000
cpu1 (AP): apic id: 1, version: 0x00030010, at 0xfee00000
io0 (APIC): apic id: 2, version: 0x000f0011, at 0xfec00000
Probing for devices on PCI bus 0:
chip0:<Intel 82434NX (Neptune)PCI cache memory controller> rev 0x11 on pci0.0.0
ncr0: <ncr 53c810 fast10 scsi> rev 0x02 int a irq 11 on pci0.1.0
...
npx0 on motherboard
npx0: INT 16 interface
Intel Pentium F00F detected, installing workaround
APIC_IO: Testing 8254 interrupt delivery
APIC_IO: routing 8254 via pin 2
changing root device to sd1s1a
SMP: AP CPU #1 Launched!
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