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Re: High interrupt CPU usage in top

To: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
From: Mark Cullen <mark.r.cullen@xxxxxxxxx>
Date: Wed, 07 Jun 2006 22:42:09 +0100

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?
: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.

Matthew Dillon <dillon@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@bone2)/usr/pkg/etc atacontrol mode 0
Master = ???
Slave  = WDMA2
(root@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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