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Hardware interrupts spiking

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Buggy Buddha View Drop Down
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    Posted: 05 September 2006 at 4:50am
I must confess I don't understand what the hardware interrupts displayed in Process Explorer are and how they work. I'd like to know if it's normal for hardware interrupts to ever spike to 50% levels (this is on a dual core system, so it's probably taking one of the cores to 100% CPU usage)? I recently noticed that this would happen when I was using a program to compare a large amount of files on DVD to the same files on HDD. The program, I think, counts hashes of files both on HDD and DVD and compares the hashes. Should something like this cause hardware interrupts to spike like that, or is it abnormal?

In general, I'd like to know what would cause hardware interrupts and how much CPU they'd normally take. TIA. :)
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Post Options Post Options   Thanks (1) Thanks(1)   Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 5:02am
Hardware interrupts occur when a peripheral wants attention from the CPU. It sounds like your DVD drive might have got into PIO transfer mode. Have a look at Interrupts spikes to 80% of CPU and see if it helps.
Gil
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buggy Buddha Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 6:24am
Thanks, I'll check if it's in PIO mode and try that solution if it is. It's a new system, though, and I don't really like the idea it would just revert to PIO mode on its own. Broken hardware? I kind of hope not, seeing how new the system is.

Is it ever normal to see hardware interrupts take a notable amount of CPU time? Or does it always imply some kind of a software/hardware issue?

Edit: one more thing, this is an XP SP 2 system.


Edited by Buggy Buddha - 05 September 2006 at 6:33am
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namrehto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 6:34am
In general interrupts shouldn't be excessive. If either they or DPCs are high it's commonly a driver issue, sometimes hardware.

From the PE help file:
"Interrupts and DPCs

On Windows NT-based systems Process Explorer shows two artificial processes: Interrupts and DPCs. These processes reflect the amount of time the system spends servicing hardware interrupts and Deferred Procedure Calls (DPCs), respectively. High CPU consumption by these activities can indicate a hardware problem or device driver bug. To see the total number of interrupts and DPCs executed since the system booted add the Context Switch column. Another sometimes useful metric is the number of interrupts and DPCs generated per refresh interval, which you see when you add the CSwitches Delta column."

It's been known for excessive read errors - apparently caused by a dodgy CD/DVD - to flip the IDE controller.
Gil
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buggy Buddha Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 6:44am
I see. I read that from the manual, but didn't quite understand whether it's always abnormal to see high CPU consumption by hardware interrupts or if it can even be expected in certain normal situations. Comparing the hashes of files has to stress the CPU, memory, and the hard drive and DVD drive alike, right? The program that did the hashing showed practically no CPU usage during the operation, but hardware interrupts stayed high. Originally, I thought it made sense, since the system was reading a lot of files from the HDD and DVD at the same time. The operation completed, too, and I didn't notice any system slowdown, though that may be just because it's a dual core system. But it'll be interesting to see if one of the devices has gone to PIO mode. If it hasn't, then it's indicative of an actual hardware failure, then? 

Edited by Buggy Buddha - 05 September 2006 at 6:45am
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namrehto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 7:26am
If an IDE controller kept reverting to PIO mode (as a result of cumulative errors) there's a possibility of a hardware issue. As a first instance checking all the cables/connectors would be a good idea, and making sure there's nothing else on the same IDE cable that could be interfering. Also confirm that the correct driver's installed (usually the standard Windows one). Manufacturer's diagnostics might help.

One wouldn't have thought that hash checking of files should be any more stressful on the interface to the DVD drive than simply copying files, and that ought to impose a pretty low interrupt load.
Gil
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buggy Buddha Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 8:31am
Looks like you were absolutely right. I checked the controller properties, and according to that, the DVD drive is in fact running in PIO mode. Windows even gave a nice warning in that menu, explaining that: "The transfer mode for this device was set to a mode lower than what it is capable of because of excessive transfer errors to that device. This will cause a loss of system performance. Please check the cabling to the device..." Nice. Going to set it back to Ultra DMA 2 mode and reboot. That does leave me to wonder what caused it to revert to PIO mode in the first place, though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Icon Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 12:37pm
My Hardware Interrupts are also showing at 50% but I do not think it's the DVD drive.I only have a Samsung CD writer/DVD reader and the IDE controllers are showing 'DMA if available'

Go easy on me as I hope I have understood the above but if I haven't please let me know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote namrehto Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 1:52pm
@Icon: Open a new thread in the Troubleshooting forum for your problem. If the interrupts are pretty much constant - i.e. don't only occur during I/O - then one would suspect an issue with sound/video, possibly a driver problem.
Gil
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buggy Buddha Quote  Post ReplyReply Direct Link To This Post Posted: 05 September 2006 at 3:23pm
Originally posted by Buggy Buddha Buggy Buddha wrote:

That does leave me to wonder what caused it to revert to PIO mode in the first place, though.


Quoting myself, but I've been trying to find the reason the DVD-drive went to PIO. I found this MS article that may be useful to others, as well: http://www.microsoft.com/whdc/device/storage/IDE-DMA.mspx

The most interesting thing I read there is this:

Quote Windows XP will turn off DMA mode for a device after encountering certain errors during data transfer operations. If more that six DMA transfer timeouts occur, Windows will turn off DMA and use only PIO mode on that device.

--

All CRC and timeout errors are logged in the system event log. These types of errors could be caused by improper mounting or improper cabling (for example, 40-pin instead of 80-pin cable). Or such errors could indicate imminent hardware failure, for example, in a hard drive or chipset.


So, any errors that cause Windows to revert to PIO mode should be logged in the system event log. My event log absolutely does not have any such log entries. So are we to assume that Windows did not switch PIO mode on because of errors, but something else happened instead?
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