# What causes high interrupt to process latency



## OBM-man (Jun 8, 2009)

I could only find the definition of this:

"The interrupt to process latency reflects the measured interval that a usermode process needed to respond to a hardware request from the moment the interrupt service routine started execution. This includes the scheduling and execution of a DPC routine, the signaling of an event and the waking up of a usermode thread from an idle wait state in response to that event."

I couldn't find information as to what would cause problems with it.
I'm using LatencyMon to measure it, and it keeps going up especially during gaming.


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## satrow (Feb 4, 2012)

The DPCs will rise during gaming, it's to be expected as at different times, hard drive access, CPU, RAM and GPU are all pushed close to their limits, as are the drivers that hook them into Windows.

Unless you have an video or audio stuttering/skipping problem, it's probably better not to even bother checking DPC latency, except to get a baseline when the PC is resting at the Desktop to ensure it's running efficiently.



> If any kernel-mode device driver in your Windows system is implemented improperly and causes excessive latencies of Deferred Procedure Calls (DPCs) then drop-outs will probably occur when you use real-time audio or video streaming applications.


^ DPC Latency Checker


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## OBM-man (Jun 8, 2009)

DPC latency isn't the problem, it's interrupt to process latency.
Is the image I posted not showing? I'll use a direct link:
http://s28.postimg.org/a4fvb1fr1/Untitled.png


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## satrow (Feb 4, 2012)

I saw the image, do you want to see some of mine? 

As I said, whilst gaming, it's normal that everything gets stressed out, there's a lot of interconnected calls and data streaming and it all has to synchronize.

What do you see when tested for a few minutes at the Desktop on idle?

What stats to you see under the other tabs in LatMon, gaming and idle?

What problems are you having?


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## OBM-man (Jun 8, 2009)

Just the interrupt to process latency acts up. It's fine when idle, but when gaming it jumps up. Other latencies are okay. DPC latency never goes past 700 μs during gaming.
There is video and audio stuttering/skipping problems in games, I'm thinking high interrupt to process latency has something to do with it.


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## satrow (Feb 4, 2012)

Well, the highest hits are from the DirectX kernel, that's not so helpful, as it could be mouse, sound, graphics ... try working through the steps here: Resplendence Software - LatencyMon: real-time audio suitability checker and the page I linked earlier to try to narrow it down.


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## OBM-man (Jun 8, 2009)

The DirectX kernel corresponds to the highest ISR routine execution time not the interrupt to process latency.
I already saw both links, neither of them says anything about interrupt to process latency.


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## satrow (Feb 4, 2012)

Ah, yes, I was looking at the wrong line. Under the Drivers tab, scroll to the highest execution column and list the top 5 - or post an image (I'll try to look at it carefully this time).

It won't hurt to follow those instructions to try to pinpoint the issue or to narrow it down. Updating drivers, etc is frequently the fix for these issues.

Your System stats are up to date, yes?


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## OBM-man (Jun 8, 2009)

Unfortunately all drivers are up to date.


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## satrow (Feb 4, 2012)

Sorry, not my day is it, could you show the Total execution times, please?

Well, especially with graphics card drivers, latest is not always the best, the most recent drivers rarely have anything new or improved to offer for previous gen. cards, except perhaps some compatibility fix for a new game.

That's where the troubleshooting steps linked earlier come into play - turn off anything vital and test, change one driver and test again, and so on.


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## OBM-man (Jun 8, 2009)

This is another instance:








I did turn off all drivers, still the same problem.


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## satrow (Feb 4, 2012)

I've just compared your stats with mine from a short gaming run earlier, the biggest difference I see is that my (ATI/AMD) graphics drivers don't show activity at all, cf. with your Nvidia at 1243ms.

Do you have DirectX 9.0C installed?

How long have you had this problem?


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## OBM-man (Jun 8, 2009)

satrow said:


> I've just compared your stats with mine from a short gaming run earlier, the biggest difference I see is that my (ATI/AMD) graphics drivers don't show activity at all, cf. with your Nvidia at 1243ms.
> 
> Do you have DirectX 9.0C installed?
> 
> How long have you had this problem?


I got DirectX 11 installed.
I started using LatencyMon only a few days ago. So I just discovered it.


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## satrow (Feb 4, 2012)

DX11 has only partial compatibility with DX9, download DirectX 9.0C from here and install it for full compatibility: Download: DirectX Redist (June 2010) - Microsoft Download Center - Download Details


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## OBM-man (Jun 8, 2009)

Thanks for the help man, but I guess it's just a problem with ****** nvidia drivers.


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