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Interrupts spikes to 80% of CPU
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guisep View Drop Down
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Posts: 2 		  Quote guisep Quote  Post ReplyReply Direct Link To This Post Topic: Interrupts spikes to 80% of CPU
    Posted: 22 August 2005 at 11:28pm
What would cause this?  Any ideas on how to debug it.  My problem started with my computer running almost always at 100%.  I've checked most things including, 3 spyware checker, 2 anti virus (none running at the same time on either).  I'm using process explorer to hopefully figure what if anything is running that I don't want.  That's when I noticed the interrupts spiking up to 80% at a time but it does cycle down to 3ish.

TIA
   Guisep
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namrehto View Drop Down
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Posts: 3861 		  Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2005 at 2:32am
Does it occur when you are doing local device I/O?  Or network I/O?

High interrupt rates on I/O are often associated with the transfer mode for an IDE device having reverted from DMA to PIO. Pre-SP2 versions of XP in particular were rather sensitive to errors and would flip to PIO mode. They needed to be reset to "DMA if available" in Device Manager, usually by uninstalling the IDE driver and letting Windows reinstall. Check out MS KB article 817472 here.

If not I/O-related then interrupts are possibly malfunction or bad connection in another device - try re-socketing connections.
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guisep View Drop Down
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Posts: 2 		  Quote guisep Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2005 at 1:29pm
IDE set to PIO.. uninstall, reboot, DMA 5... yeah fast system again!

Thanks so much I would have never looked there.. 
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namrehto View Drop Down
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Posts: 3861 		  Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2005 at 2:38pm
Glad you got it fixed.
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tashkerm View Drop Down
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Posts: 4 		  Quote tashkerm Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2005 at 12:40am
And thank you, too, namrehto.  Just had the same problem with a new Dell laptop, h/w interrupts spiking at 80%: slooooow.  Followed your instructions:  faaaast.
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namrehto View Drop Down
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Posts: 3861 		  Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2005 at 3:40am
Great. Surprising this should happen with a new laptop, presumably shipping with XP SP2. The issue with Windows driver error sensitivity originally arose pre SP2. If the syndrome keeps repeating then return the laptop for service as it would suggest a potential hardware problem.
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tashkerm View Drop Down
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Posts: 4 		  Quote tashkerm Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2005 at 1:15pm

Interesting you mention that.

I didn't want to provide the (long and boring) story, but the new laptop did have a hardware problem (occasionally didn't complete POST, and more) resulting in a new motherboard.  I suspect the h/w problems forced the OS to change the driver into PIO mode, and it stayed that way even after the m/b was replaced.  But that's pure speculation, probably not worth the bytes it's printed on.

Both h/w and s/w are now doing fine.
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namrehto View Drop Down
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Posts: 3861 		  Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2005 at 1:35pm
I suspect the h/w problems forced the OS...

Probably an accurate conjecture. If the mobo problems tripped the switch to PIO, then it would of course have survived mobo replacement. The transfer mode is only a registry setting.

Both h/w and s/w are now doing fine.

May they live together happily ever after.
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shanimal View Drop Down
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Posts: 4 		  Quote shanimal Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2006 at 2:23pm

Hello-

Thank you Process Explorer and this forum! We had a workstation that was constantly getting bogged down and I tried just about everything I could think of to speed things up. Not until PE identified the interrupts as the culprit, and a search of this forum did I get the priblem solved! The Primary IDE controller was in PIO mode. Uninstalled with Device manager, reboot, reboot again, and the system is back to Ultra DMA mode and running without getting bogged down. Great stuff, thanks alot Mark and everybody else who contributes to this forum.

Phil
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otistdog View Drop Down
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Posts: 17 		  Quote otistdog Quote  Post ReplyReply Direct Link To This Post Posted: 07 November 2006 at 3:49pm
Originally posted by namrehto


Does it occur when you are doing local device I/O?

Or network I/O?

High interrupt rates on I/O are often associated with the transfer mode
for an IDE device having reverted from DMA to PIO. Pre-SP2 versions of XP
in particular were rather sensitive to errors and would flip to PIO
mode. They needed to be reset to "DMA if available" in Device Manager,
usually by uninstalling the IDE driver and letting Windows reinstall.
Check out MS KB article 817472 here.


Namrehto,

Why did you ask about network I/O activity on this? I'm still chasing some intermittent slowdowns, and it doesn't seem to be related to the DMA/PIO setting.

Is there additional wisdom about network card I/O impact that you'd like to share?

--Otis


Edited by otistdog - 09 November 2006 at 3:08pm
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