High interrupt load on VIA C3 machine
Bruce Cran
bruce at cran.org.uk
Fri Aug 31 12:54:52 PDT 2007
Bruce Cran wrote:
> I recently upgraded to 7-CURRENT on my VIA EPIA router, and have found
> that there's a constant interrupt load of around 15%. My dmesg
> reports the CPU as:
>
> CPU: VIA C3 Nehemiah+RNG+AES (533.36-MHz 686-class CPU)
> Origin = "CentaurHauls" Id = 0x698 Stepping = 8
>
> Features=0x381b93f<FPU,VME,DE,PSE,TSC,MSR,CX8,SEP,MTRR,PGE,CMOV,PAT,MMX,FXSR,SSE>
>
> real memory = 132055040 (125 MB)
> avail memory = 119701504 (114 MB)
>
> uname -a:
> FreeBSD router.draftnet 7.0-CURRENT FreeBSD 7.0-CURRENT #4: Fri Aug 31
> 07:04:22 BST 2007
> brucec at router.draftnet:/usr/obj/usr/src/sys/ROUTER i386
>
> The first few lines of top -S are:
> last pid: 1394; load averages: 0.08, 0.12,
> 0.21
> up 0+01:59:10 16:13:59
> 57 processes: 3 running, 39 sleeping, 15 waiting
> CPU states: 3.1% user, 0.0% nice, 4.8% system, 17.0% interrupt,
> 75.1% idle
> Mem: 7360K Active, 6116K Inact, 12M Wired, 48K Cache, 9504K Buf, 90M Free
> Swap: 2048M Total, 2048M Free
>
> PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND
> 11 root 1 171 ki31 0K 8K RUN 100:01 81.98% idle
> 12 root 1 -32 - 0K 8K WAIT 12:31 7.96% swi4:
> clock sio
> 1394 brucec 1 46 0 3512K 1744K RUN 0:01 4.98% top
> 586 root 1 44 0 5016K 2516K RUN 2:39 0.00% ppp
> 1044 root 1 44 0 3176K 980K select 0:51 0.00% powerd
> 28 root 1 -68 - 0K 8K WAIT 0:45 0.00% irq11:
> vr0 dc3
> 30 root 1 -68 - 0K 8K WAIT 0:32 0.00% irq12: dc1
>
> While there's a high interrupt load, vmstat -i doesn't show anything
> wrong:
>
> interrupt total rate
> irq0: clk 718003 99
> irq4: sio0 897 0
> irq5: dc0 31 0
> irq8: rtc 919064 127
> irq10: dc2 uhci0+ 31 0
> irq11: vr0 dc3 63548 8
> irq12: dc1 62120 8
> irq14: ata0 1555 0
> irq15: ata1 581 0
> Total 1765830 245
>
> I had thought of using hwpmc to find out what was happening, but
> unfortunately VIA CPUs aren't supported yet. Is there another way I
> can find out what's going on?
This appears to be an issue with powerd/cpufreq - disabling powerd
reduces the interrupt load to a couple of percent at most, and the clock
interrupt task now only accumulates CPU time very slowly (previously it
was using 7% CPU all the time).
--
Bruce Cran
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