Re: ICH5 SATA causes high interrupt/system load?

Jeff Garzik (jgarzik@pobox.com)
Wed, 02 Jul 2003 19:07:12 -0400


Jurgen Kramer wrote:
> BTW it seems that all ATA ports have their own interrupt:
>
> CPU0 CPU1
> 14: 5062 5316 IO-APIC-edge ide0
> 15: 1 1 IO-APIC-edge ide1
> 16: 43464 43565 IO-APIC-level usb-uhci, usb-uhci, nvidia
> 17: 26180 26194 IO-APIC-level Intel ICH5
> 18: 119342344 119704504 IO-APIC-level ide2, usb-uhci

The interrupt count is definitely high.

WRT the interrupt distribution through, the above is normal. irq 14 and
15 are the magic legacy IDE interrupts. Anything other than 14 and 15
are (usually) standard shareable PCI interrupts.

> 20:08:28 up 19 min, 3 users, load average: 0.08, 0.06, 0.02
> 75 processes: 74 sleeping, 1 running, 0 zombie, 0 stopped
> CPU0 states: 0.5% user 20.2% system 0.0% nice 0.0% iowait 78.2%
> idle
> CPU1 states: 0.5% user 17.0% system 0.0% nice 0.0% iowait 81.4%
> idle
> Mem: 515128k av, 187396k used, 327732k free, 0k shrd, 13336k
> buff
> 45524k active, 118320k inactive
> Swap: 787176k av, 0k used, 787176k free 90804k
> cached
>
> With your patch and in XP a have a nice nullish system load.

Very strange. My first guess would be that the drivers/ide driver
appears unfriendly to shared interrupts. In certain cases the ATA
protocol does not offer a single, easy "is this interrupt mine?" test;
the logic has to be implicitly worked into the driver code. However,
normally the drivers/ide driver knows what the heck it is doing, so this
is quite out of the ordinary.

Perhaps you can fiddle with BIOS settings to get ide2 onto an interrupt
all by itself, and see if the behavior improves.

Jeff

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