irq19 uhci interrupts taking ~100% of one core?
kg5nm at comcast.net
Sat Sep 20 15:44:12 UTC 2008
I think this is a SATA driver problem on amd64 builds. I have the same
problem (3 usable cores due to this!). I'm too am running a custom kernel
but this was also happening on GENERIC.
If you temporarily disable all USB drivers, you should see the SATA ATAPI
driver pop up on 'vmstat -i' instead of UHCI. IRQ 19 is a multi-use IRQ and
vmstat reports one IRQ grabber.
An additional clue: I unplugged 3 of my 4 SATA drives and the 'IRQ shower'
actually increased about 25%!
I'm considering posting this to the -CURRENT folks to see if this is being
worked, it's pretty painful to lose 25% of my quad-core just to this
interrupt shower; FYI - I'm calling it a 'shower' since it's not bad enough
for the kernel to flag it as a storm. :)
- Gary (kg5nm at comcast.net)
Scott Gasch wrote:
> Replying to my own question with more data.
> Previously I had been running my own kernel; I was curious if the problem
> would reproduce with a GENERIC kernel. It does but the symptoms are
> slightly different. The same irq is firing too often and consuming nearly
> all of one core. But the driver that is associated with the interrupt is
> different -- it's fwohci0:
> interrupt total rate
> irq6: fdc0 1 0
> irq17: mskc0 dc0 313242 13
> irq18: skc0 uhci2* 124475451 5540
> irq19: fwohci0+++ 957875379 42638
> irq23: uhci3 ehci1 1145 0
> cpu0: timer 44458513 1979
> cpu1: timer 44448875 1978
> cpu3: timer 43393901 1931
> cpu2: timer 43393921 1931
> Total 1258360428 56014
> This makes me start to wonder if this is not a problem with irq19 (the
> and not one particular device / driver. I'm not sure how to make dig
> here, any help greatly appreciated.
> On Sun, Sep 7, 2008 at 4:07 PM, Scott Gasch <scott.gasch at gmail.com> wrote:
>> I'm running freebsd 7.0-RELEASE-p4 on a 4-core amd64 box. nearly 100% of
>> cpu is constantly being used handling irq19: uhci4 interrupts. This
>> to happen both with and without any USB devices plugged in:
>> vmstat -i
>> interrupt total rate
>> irq1: atkbd0 5 0
>> irq6: fdc0 1 0
>> irq17: mskc0 dc0 1180547 18
>> irq18: skc0 uhci2* 163250699 2512
>> irq19: uhci4++ 3187989508 49072
>> irq23: uhci3 ehci1 31 0
>> cpu0: timer 129208570 1988
>> cpu1: timer 129208457 1988
>> cpu2: timer 125750147 1935
>> cpu3: timer 125750122 1935
>> Total 3862338087 59452
>> uhci4: <UHCI (generic) USB controller> port 0xa400-0xa41f irq 19 at
>> on pci0
>> uhci4: [GIANT-LOCKED]
>> uhci4: [ITHREAD]
>> Any idea what's going on here and/or how to fix this?
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