2 processes Task Manager

  • Thread starter Thread starter Bill in Co.
  • Start date Start date
Farhan said:
I am seeing two process in process explorer:
1- interrupts - hardware interrupts
2- DPCs - Deferred Procedure Calls

They both take CPU very often. What are they?
Click to expand...

An interrupt is a signal the hardware sends to the CPU,
when it needs the CPU's attention. The CPU runs an
"interrupt handler", to take care of the needs of the
hardware that raised the interrupt. Some events are
asynchronous, such as when a packet is received on
your Ethernet interface. When the packet arrives, the
CPU needs to be told. An interrupt is a good way to
do that. The interrupt, as the name implies, causes
the processor to stop doing what it is currently
doing, and pay attention to the hardware needing
service. Once the interrupt handler is finished, the
CPU returns to the application it was working on.

The DPC is described here.

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

The use of DPC, allows hardware servicing to be
split into two pieces. The Interrupt Handler portion
can have a short runtime, and only the most critical
things are done there. Less critical things are
scheduled for later execution, and that is where the
DPC comes in. The DPC concept has been around for a
while, and I think a software person in my group,
described it to me somewhere around 1985 or so.

If the entire handler ran at interrupt level, it would
make the OS less responsive.

Paul
 
I am seeing two process in process explorer:
1- interrupts - hardware interrupts
2- DPCs - Deferred Procedure Calls

They both take CPU very often. What are they?
 
Paul said:
An interrupt is a signal the hardware sends to the CPU,
when it needs the CPU's attention. The CPU runs an
"interrupt handler", to take care of the needs of the
hardware that raised the interrupt. Some events are
asynchronous, such as when a packet is received on
your Ethernet interface. When the packet arrives, the
CPU needs to be told. An interrupt is a good way to
do that. The interrupt, as the name implies, causes
the processor to stop doing what it is currently
doing, and pay attention to the hardware needing
service. Once the interrupt handler is finished, the
CPU returns to the application it was working on.

The DPC is described here.

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

The use of DPC, allows hardware servicing to be
split into two pieces. The Interrupt Handler portion
can have a short runtime, and only the most critical
things are done there. Less critical things are
scheduled for later execution, and that is where the
DPC comes in. The DPC concept has been around for a
while, and I think a software person in my group,
described it to me somewhere around 1985 or so.

If the entire handler ran at interrupt level, it would
make the OS less responsive.

Paul
Click to expand...

There is an example here, of someone with high interrupt/DPC,
and it was related to UAA/HDaudbus.sys.

http://forum.sysinternals.com/forum_posts.asp?TID=12982&PID=59372

Paul
 
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