On Mon, Jan 10, 2022 at 10:36:41AM -0500, Ryan Kavanagh wrote:
> >Synopsis: high interrupt processing time on Dell Latitude E7450
> >Category: kernel amd64
> >Environment:
> System : OpenBSD 7.0
> Details : OpenBSD 7.0-current (GENERIC.MP) #242: Sat Jan 8
> 12:33:38 MST 2022
>
> dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
>
> Architecture: OpenBSD.amd64
> Machine : amd64
> >Description:
>
> I installed OpenBSD 7.0 on a Dell Latitude E7450. The installer had me
> using GENERIC, and interrupts hovered above 40%-45% when idle. I
> upgraded to 7.0-current with the same issue. The laptop ran hot,
> presumably as a result of the high interrupt processing time.
>
> Here is the output of vmstat -i under 7.0-current / GENERIC:
>
> interrupt total rate
> irq0/clock 885333 99
> irq96/acpi0 1789 0
> irq144/inteldrm0 117024 13
> irq114/em0 12414 1
> irq176/azalia1 1668 0
> irq115/iwm0 416586 47
> irq102/ehci0 221 0
> irq103/ahci0 124340 14
> irq104/ichiic0 1770 0
> irq145/pckbc0 17710 1
> irq146/pckbc0 44588 5
> Total 1623443 183
>
> Stuart Henderson suggested in the misc thread [0] that I try GENERIC.MP.
> After switching, top shows that CPU0 is spending roughly the same amount
> of time processing interrupts, while CPU1 is free to do other stuff.
> Representative capture:
>
> CPU0 states: 18.6% user, 0.0% nice, 3.0% sys, 0.2% spin, 44.3% intr,
> 33.9% idle
> CPU1 states: 50.3% user, 0.0% nice, 5.0% sys, 1.6% spin, 0.0% intr,
> 43.1% idle
>
> `systat vm` shows an Int% hovering around 20% (I imagine it's the mean
> of the two interrupt rates shown by top), with lows in the low 10% and
> highs in the low 30%.
>
> My laptop does not seem to get as hot as quickly under GENERIC.MP, but
> it still gets pretty hot: hw.sensors.cpu0.temp0=86.00 degC after 5
> minutes when watching a video on Youtube in firefox.
>
> vmstat -i under GENERIC.MP after being up ~35 minutes with light load:
>
> interrupt total rate
> irq0/clock 860124 399
> irq0/ipi 714019 331
> irq96/acpi0 436 0
> irq144/inteldrm0 33945 15
> irq114/em0 7965 3
> irq176/azalia1 1 0
> irq115/iwm0 73471 34
> irq102/ehci0 73 0
> irq103/ahci0 44676 20
> irq104/ichiic0 431 0
> irq145/pckbc0 6441 2
> irq146/pckbc0 3178 1
> Total 1744760 810
>
> I ran
>
> btrace -e 'profile:hz:100 { @[kstack] = count(); }' > /tmp/btrace.out
>
> for ten seconds and ran the output through
>
> https://github.com/brendangregg/FlameGraph/raw/master/stackcollapse-bpftrace.pl
> https://github.com/brendangregg/FlameGraph/raw/master/flamegraph.pl
>
> The output of stackcollapse-bpftrace.pl and flamegraph.pl are attached
> as btrace.collapsed and btrace.svg.
The flamegraph suggests that you spent 10% of that time servicing
ichiic(4) interrupts from idle.
That could be a fluke though.
What does the main systat view look like in the interrupt column?
$ systat 1
