> Yet another thing which would be interesting. Load the i915 module and run
> the userland graphics stack. Open the serial port for read, which should
> not result in any interrupts. Check /proc/interrupts for the number of
> interrupts for the serial port,
Hmm, the 8250 driver will generate one interrupt even when just reading.
> wait 10 seconds and check again. In theory the numbers should be the
> same. My crystal ball tells me they are not.
root@test:~# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz root=/dev/sda1 rootwait ro quiet nolapic=1
root@test:~# uname -r
4.18.17
root@test:~# lsmod | grep i915
i915 1544192 2
drm_kms_helper 159744 1 i915
drm 376832 4 drm_kms_helper,i915
intel_gtt 24576 1 i915
root@test:~# cat /proc/interrupts ; sleep 10; cat /proc/interrupts
CPU0
0: 16835 XT-PIC timer
1: 5 XT-PIC i8042
2: 0 XT-PIC cascade
4: 1 XT-PIC ttyS0
5: 1247 XT-PIC eth0
6: 343 XT-PIC snd_hda_intel:card0
8: 1 XT-PIC rtc0
9: 4 XT-PIC acpi
10: 4627 XT-PIC ahci[0000:00:1f.2], i801_smbus
11: 358 XT-PIC PCIe PME, pciehp, ehci_hcd:usb1, xhci-hcd:usb2, i915
12: 7 XT-PIC i8042
NMI: 0 Non-maskable interrupts
LOC: 0 Local timer interrupts
SPU: 0 Spurious interrupts
PMI: 0 Performance monitoring interrupts
IWI: 0 IRQ work interrupts
RTR: 0 APIC ICR read retries
RES: 0 Rescheduling interrupts
CAL: 0 Function call interrupts
TLB: 0 TLB shootdowns
TRM: 0 Thermal event interrupts
THR: 0 Threshold APIC interrupts
MCE: 0 Machine check exceptions
MCP: 3 Machine check polls
ERR: 22872
MIS: 0
PIN: 0 Posted-interrupt notification event
NPI: 0 Nested posted-interrupt event
PIW: 0 Posted-interrupt wakeup event
CPU0
0: 16998 XT-PIC timer
1: 5 XT-PIC i8042
2: 0 XT-PIC cascade
4: 1 XT-PIC ttyS0
5: 1257 XT-PIC eth0
6: 343 XT-PIC snd_hda_intel:card0
8: 1 XT-PIC rtc0
9: 4 XT-PIC acpi
10: 4631 XT-PIC ahci[0000:00:1f.2], i801_smbus
11: 358 XT-PIC PCIe PME, pciehp, ehci_hcd:usb1, xhci-hcd:usb2, i915
12: 7 XT-PIC i8042
NMI: 0 Non-maskable interrupts
LOC: 0 Local timer interrupts
SPU: 0 Spurious interrupts
PMI: 0 Performance monitoring interrupts
IWI: 0 IRQ work interrupts
RTR: 0 APIC ICR read retries
RES: 0 Rescheduling interrupts
CAL: 0 Function call iroot@test:~# cat /proc/cmdline
TLB: 0 TLB shootdowns
TRM: 0 Thermal event interrupts
THR: 0 Threshold APIC interrupts
MCE: 0 Machine check exceptions
MCP: 3 Machine check polls
ERR: 23049
MIS: 0
PIN: 0 Posted-interrupt notification event
NPI: 0 Nested posted-interrupt event
PIW: 0 Posted-interrupt wakeup event
(same setup as in previous mail, X11 was running with the Qt4 GUI
application in OpenBox)
What I'm wondering is about the massive number of ERR interrupts ...
root@test:~# while sleep 1; do grep ERR: /proc/interrupts ; done
ERR: 25786
ERR: 25809
ERR: 25837
ERR: 25861
ERR: 25890
ERR: 25912
^C
This is specific to nolapic=1, with "noapic=1" the ERR interrupt number
stays at 51. But I guess this is a red herring, too, because who runs
his box with nolapic=1 in the first place :-)
Greetings,
Holger
