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How to get the cause of high CPU usage by DPC / Interrupt


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I had a conversation with the author of LatencyMon. He first told me

"The interrupt-to-latency test is only meaningful without having any other programs running in the background."

to which I replied

"You say it's only meaningful without having any other programs running but my concern is that if I'm getting high latency spikes when certain activity happens, such as writing to disk, then these spikes are going to cause issues with audio/video when this activity happens whilst using A/V software, gaming, etc."

and he replied

"The interrupt-to-latency monitor simulates a critical audio process. This is why it is not recommended to be running any other activity on top.

That said, if you would like to paste the contents of the report view in a message, we don’t mind to take a look to see if there is anything peculiar in your system."

So I sent him three reports, one at idle, one launching Iron and one launching Mediaportal

and he replied

"Your system appears to be OK. Regarding excessive hard disk usage and spikes under load, I suggest you make sure that your harddisks have enough free space and are not fragmented. You can use the standard Windows defragmentation tool for that. If fragmentation on your system is low and not a problem then I suggest considering if excessive paging might be the problem (take a look at your memory load, kill of processes that consume a lot of memory, etc.)"

My HDDs are defragged and have plenty of space, so that's not an issue. I also told him that I see tons of hard pagefaults from svchost.exe when analysing the disk with Windows defrag but no latency spikes and he replied

"Whether they are connected depends on the priority of the process that incurs the page fault. Defrag runs at lower or idle priority. In principle, only a real-time priority process/thread can compete and thus influence the interrupt to process latency measurements."

Which makes sense, although it doesn't get me any nearer to understanding why I'm getting latency spikes with MediaPortal, where it does matter as that's for playing media and having spikes during that could cause audio/video glitches. I guess I should ask on the MediaPortal forums if anyone knows anything about that.

Edited by doveman
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Hi MagicAndre1981,

thanks for your good explanation however i believe the Windows Performance Tools Kit has at least a little changed since you wrote your first post (i was not able to select "Load Symbols" after i had selected an interval). And so i did not really find the summary of all calls page.

So i used LatencyMon as you suggested and found that "ACPI.sys" was in fact the cause of the high CPU load. In my case the high CPU load did not always start after booting (only around 50% of the time) sometimes it would only start short after starting any 3D intensive program and then stay until I either restart (50/50 gamble :) ) or go into energy saving mode and reactivate my notebook. So i first i disabled CPU throttling and uninstalled Asus' "Power4Gear" (which adds additional power saving plans to the windows ones) together with a bunch of other pre-installed software. That unfortunately did not change anything.

Of course I proceeded with the second step you in that case always suggested (updating the BIOS) ... AND THAT DID IT !

I hope that will help others in the future.

And of course ...THANK YOU VERY MUCH MagicAndre1981 for the time and work you invest to help!

(I also attached some system information and two LatencyMon screenshots)

ASUS K53SV

Win 7 64Bit

Intel Core i5-2410M

GeFOrce GT 540M CUDA 2GB

8GB RAM

one 500GB s-ata HDD

post-380033-0-01820300-1374359207_thumb. post-380033-0-09016100-1374359211_thumb.

Edited by testmail123abc
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  • 2 months later...

Hello there,
first I would like to tank you for this topic and for your effor to try to help others.
I have asus k53sc, intel i3, 4gb ram, Geforce mx 520. WIn 7 proffesional

I have OS on ssd disc solo and instead of my DvD I have hard disk.
I have High CPU usage ( 1 of the 4 threads ) is running on 100% most of the time. It starts after I play for some time a game. (WoT, WoW, LoL, AC, anything ) Sometimes it start after 2 minutes sometimes immediately.

I've tried program procexp because it can shut a proces down... it didint work.
Then I tried that it might be doing screwes in motherboard.... so I carefully disambled notebook and turned it on without screwes and it didint work either. I have tried to re-aply the cooling past on CPU and clean the notebook. I have tried formating the system I have installed every driver u can think of, BIOS chipset, graphic card, sound card everything. I tried to disalble special soundeffects coz I have found that it helped someone. Didn't work.
Then I have found your thread and found out that it is probably causing ACPI.sys . Read whole thread and havent found anything that would help me.
Here is my DPC file with the txt exported one.

http://uloz.to/xWrFZXYt/dpc-interrupts-4-rar

I really appriciate what you are doing here and I am looking forward to your advice.

Spotak

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use Speedfan to increase the speed of the CPU fans to cool down the CPU. Does this improve the situation?

I was really trying b ut I can't see my fan in speedfan and really don't know how to add it there... I know I have 1 fan there but could you help me please?

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