High interrupt CPU usage in top

[Matthew Dillon]

: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?

    IDE doesn't really support devices that are only on the slave, with
    no master.  At least, not reliably.  You have to make both of them
    the master. 

    It is either the cable or a jumper on the drive.   Try fixing that and
    see if it boots with DMA turned on.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>