High interrupt CPU usage in top

Mark Cullen mark.r.cullen at gmail.com
Wed Jun 7 14:42:09 PDT 2006


Matthew Dillon wrote:
:Well, world and kernel just finished compiling, without INVARIANTS, and 
:there's no difference. Infact, it seems worse... but it's probably the 
:same. I guess I should keep INVARIANTS in for debugging in case of panics?
:
:http://img198.imageshack.us/img198/1571/interrupt3eg.jpg
:
:40% and very few interrupts? That was just starting out compiling 
:`mysql4-server`.

    INVARIANTS is pretty light weight, it won't make much of a difference.

    Try doing some basic tests to exercise JUST the network adapter, like
    running a 'ping -i 0.1 <target>'.  And some tests to exercise JUST your
    hard disk, like doing a few cpdup's or a tar or something.
    If its the disk, check your dmesg output to whether the ATA driver is
    using DMA or not.
					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>
Well, `ping -i 0.1 <t>` got me less than 1%. However, `ping -f <t>` got 
me 35%.

As for disk, a very simple `dd if=/dev/<d> of=/dev/null` gets me ~25%, 
and as far as I can see DMA is enabled.

---
(root at bone2)/usr/pkg/etc atacontrol mode 0
Master = ???
Slave  = WDMA2
(root at bone2)/usr/pkg/etc atacontrol mode 1
Master = ???
Slave  = UDMA33
---
As you can see, a bit of a mix up there, CD drive is primary slave and 
the hard disk is secondary slave. However, before you blame it on 
this... my last install (just yesterday actually) was a 30GB disk on 
primary master and has the exact same behaviour.

I ran the same commands on the 4.11 box (different motherboard / chipset 
but that's it) and `ping -f <t>` is around 17% and the simple dd is the 
same, +- a few percent. Both have polling enabled, and both are using 
identical Intel NIC's, two in each machine.

Any of that info is worth anything to anyone?





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