John Sigler wrote:
I'm using a -rt kernel with high resolution timer support.
http://rt.wiki.kernel.org/index.php/Main_Page
Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT
RT Tue Oct 9 10:02:45 CEST 2007
I enabled high resolution timer support and disabled ACPI support.
CONFIG_TICK_ONESHOT=y
# CONFIG_NO_HZ is not set
CONFIG_HIGH_RES_TIMERS=y
CONFIG_GENERIC_CLOCKEVENTS_BUILD=y
# CONFIG_SMP is not set
...
CONFIG_PREEMPT_RT=y
CONFIG_PREEMPT=y
CONFIG_PREEMPT_SOFTIRQS=y
CONFIG_PREEMPT_HARDIRQS=y
CONFIG_PREEMPT_BKL=y
# CONFIG_CLASSIC_RCU is not set
CONFIG_PREEMPT_RCU=y
# CONFIG_RCU_TRACE is not set
CONFIG_X86_UP_APIC=y
CONFIG_X86_UP_IOAPIC=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_X86_IO_APIC=y
...
CONFIG_MTRR=y
CONFIG_REGPARM=y
# CONFIG_SECCOMP is not set
CONFIG_HZ_100=y
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=100
High resolution timers do not work in this configuration.
Any idea why?
# cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc pit jiffies
# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc
My timestamp counter is good. Why do I need ACPI for hrt?
I noticed something strange about IRQ0.
It keeps firing even after the system has booted.
# cat /proc/interrupts ; sleep 10 ; cat /proc/interrupts
CPU0
0: 312530 IO-APIC-edge timer
2: 0 XT-PIC-XT cascade
4: 73 IO-APIC-edge serial
8: 1 IO-APIC-edge rtc
15: 16085 IO-APIC-edge ide1
16: 3302 IO-APIC-fasteoi eth0
17: 1560 IO-APIC-fasteoi eth1
18: 1560 IO-APIC-fasteoi eth2
19: 1560 IO-APIC-fasteoi eth3
NMI: 0
LOC: 312489
ERR: 0
MIS: 0
CPU0
0: 313532 IO-APIC-edge timer
2: 0 XT-PIC-XT cascade
4: 73 IO-APIC-edge serial
8: 1 IO-APIC-edge rtc
15: 16109 IO-APIC-edge ide1
16: 3309 IO-APIC-fasteoi eth0
17: 1565 IO-APIC-fasteoi eth1
18: 1565 IO-APIC-fasteoi eth2
19: 1565 IO-APIC-fasteoi eth3
NMI: 0
LOC: 313492
ERR: 0
MIS: 0
IRQ0 is still firing. (1002 times in 10 s = 100 Hz)
When high resolution timers work, the IRQ0 counter stops incrementing
after the system has booted. (When the system switches from the PIT to
the APIC timer AFAIU.) The APIC timer (is that what LOC counts?) also
fired 1003 times in 10 s = 100 Hz.
Is it normal that both the PIT and the APIC timer keep firing?
Regards.
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