Troubleshooting heavy DPC (Deferred Procedure Calls) use?

[BillW50]

Yesterday on this netbook, Process Explorer showed that DPC was eating
50% or more CPU time. The machine was really slow and sluggish. I
cheated and restored from an earlier backup and all is well again.
Although I did also saved a backup of it acting up all of the time. So I
would like to try to troubleshoot it if for nothing else for educational
purposes. But I don't know how to troubleshoot DPC problems. I believe a
Windows update, touchpad driver update, or something else may have
caused the original problem. Any ideas?

 

[Jose]

Yesterday on this netbook, Process Explorer showed that DPC was eating
50% or more CPU time. The machine was really slow and sluggish. I
cheated and restored from an earlier backup and all is well again.
Although I did also saved a backup of it acting up all of the time. So I
would like to try to troubleshoot it if for nothing else for educational
purposes. But I don't know how to troubleshoot DPC problems. I believe a
Windows update, touchpad driver update, or something else may have
caused the original problem. Any ideas?

Hard to troubleshoot when it is behaving.

Google result show that people are sometimes instantly happy with
manipulating their ACPI battery settings in Device Manager or merely
removing their battery temporarily - with some happy faces when the
miracle occurs. Sounds very ACPI/battery related, but I have never
seen this problem.

Other folks use Vista only tools to isolate it to a few specific driver
(s) and I don't know what XP equivalents might be.

 

[Paul]

Yesterday on this netbook, Process Explorer showed that DPC was eating
50% or more CPU time. The machine was really slow and sluggish. I
cheated and restored from an earlier backup and all is well again.
Although I did also saved a backup of it acting up all of the time. So I
would like to try to troubleshoot it if for nothing else for educational
purposes. But I don't know how to troubleshoot DPC problems. I believe a
Windows update, touchpad driver update, or something else may have
caused the original problem. Any ideas?

A large number of DPCs, could come from a large number of hardware
interrupts. But that might not be the only mechanism.

http://en.wikipedia.org/wiki/Deferred_Procedure_Call

Another measure of "badness", is DPC Latency. That is a
measurement of the service time for a DPC. On some computers,
even when there are only a handful of DPCs being serviced, some
of them see a 10 millisecond delay, instead of the normal
hundreds of microseconds delay, in getting serviced.
Something that can cause a high latency, is this.

http://en.wikipedia.org/wiki/System_management_interrupt

The OS doesn't know it is happening, but the symptoms can be
observed. Sometimes a BIOS update fixes it. This tool can be
used, to detect a latency problem (caused by an invisible,
unscheduled activity, stealing the processor).

http://www.thesycon.de/deu/latency_check.shtml

In your case, I would have fired up the Performance plugin and
looked at interrupt counts. Your problem isn't latency, as
much as it is the sheer number of them.

Paul

 

[BillW50]

In
Jose typed on Thu, 1 Oct 2009 11:53:59 -0700 (PDT):

Hard to troubleshoot when it is behaving.

Google result show that people are sometimes instantly happy with
manipulating their ACPI battery settings in Device Manager or merely
removing their battery temporarily - with some happy faces when the
miracle occurs. Sounds very ACPI/battery related, but I have never
seen this problem.

Other folks use Vista only tools to isolate it to a few specific
driver (s) and I don't know what XP equivalents might be.

In Paul typed on Thu, 01 Oct 2009 17:35:41 -0400:

A large number of DPCs, could come from a large number of hardware
interrupts. But that might not be the only mechanism.

http://en.wikipedia.org/wiki/Deferred_Procedure_Call

Another measure of "badness", is DPC Latency. That is a
measurement of the service time for a DPC. On some computers,
even when there are only a handful of DPCs being serviced, some
of them see a 10 millisecond delay, instead of the normal
hundreds of microseconds delay, in getting serviced.
Something that can cause a high latency, is this.

http://en.wikipedia.org/wiki/System_management_interrupt

The OS doesn't know it is happening, but the symptoms can be
observed. Sometimes a BIOS update fixes it. This tool can be
used, to detect a latency problem (caused by an invisible,
unscheduled activity, stealing the processor).

http://www.thesycon.de/deu/latency_check.shtml

In your case, I would have fired up the Performance plugin and
looked at interrupt counts. Your problem isn't latency, as
much as it is the sheer number of them.

Paul

Thanks Jose and Paul for your very informative information! I believe I
nailed down what the problem is on this one machine. When you get 18
inches or closer to another machine with WiFi, DPCs use goes up
drastically.