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


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I managed to get the DPC latency under controlling by disabling all the ASUS services and stopping AI Suite.exe from loading and then I get something like this at idle:


However, when i went to copy some 45GB from my other PC over the LAN, it went to hell:


When it's transferring slowly (FreeFileSync showing around 5 KB/s, which I presume is because there's a lot of small files so it can't build up speed or something) then this doesn't happen but as soon as it goes up to 5-10 MB/s then boom!

I made another trace over a minute whilst the file transfer was running (without LatencyMon of course), which might show something I guess:


I downloaded a few older drivers to test, 18.5, 18.7, 18.8.1 but none of them work with my hardware and the only one that worked was 19.0 (the latest is 19.1). It didn't make any difference to my problem unfortunately.

EDIT: It seems if I put the Power setting to High Performance, so that the CPU runs constantly at 4400Mhz, then I don't get any latency spikes when transferring files. Switching back to Balanced and I couldn't seem to trigger the problem copying with Explorer but with FreeFileSync, once it hit about 20 MB/s it happened, likewise with Teracopy.

EDIT2: Seems even High Performance doesn't quite solve the problem. I wasn't even transferring files when this happened so it seems to have been caused by browsing:


Edited by doveman
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It doesn't happen when I run in High Performance though. If it's normal when transferring a lot of data, it would mean it happens when streaming video or maybe playing online games and would cause stuttering, etc, so I don't think it can be normal.

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  • 2 weeks later...

Hello Andre, as i mentioned in pm. just a quick summary, ive been having some issues with dpc latency causing some audio popping and stutter while gaming. ive searched all over the web for a solution to this. i have run latency mon and the main drivers at the top of the list are usually nvidia drivers, directx, usbport.sys, ataport.sys, tcpip.sys, etc. the issues im having primarily show up when i am playing a game and mostly while playing in nvidia surround mode on 3 Asus monitors. should i do the trace while im gaming or should i do it while my pc is idle or should i get a trace of both for you to review to help me isolate the issue?

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the idle trace shows some DPC issues caused by the nVIDIA GPU driver:

Total = 50848 for module nvlddmkm.sysElapsed Time, >        0 usecs AND <=        1 usecs,    903, or   1.78%Elapsed Time, >        1 usecs AND <=        2 usecs,   8468, or  16.65%Elapsed Time, >        2 usecs AND <=        4 usecs,  10120, or  19.90%Elapsed Time, >        4 usecs AND <=        8 usecs,   7422, or  14.60%Elapsed Time, >        8 usecs AND <=       16 usecs,  17104, or  33.64%Elapsed Time, >       16 usecs AND <=       32 usecs,   5847, or  11.50%Elapsed Time, >       32 usecs AND <=       64 usecs,    678, or   1.33%Elapsed Time, >       64 usecs AND <=      128 usecs,     29, or   0.06%Elapsed Time, >      128 usecs AND <=      256 usecs,      0, or   0.00%Elapsed Time, >      256 usecs AND <=      512 usecs,    271, or   0.53%Elapsed Time, >      512 usecs AND <=     1024 usecs,      6, or   0.01%Total,                                                 50848

In the gaming the Spikes of the nVIDIA driver are larger.


You still use the 337.88 driver, try the 340.52:




and look if this improves it.

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I've just done a fresh install of Win 8.1 Update 1 x64 on another system, AMD not Intel this time and have the same issue with ndis.sys causing massive latency spikes when in Balanced mode, which is fixed by running in High Performance mode, so it seems a common issue across all platforms when using power saving features.


I guess if playing an online video is enough to keep the CPU in High Power state then it won't cause any problems but if it's fluctuating between states (and certainly a youtube video shouldn't need a 4-core 4670k to run at 3.8Ghz (or 4.4Ghz overclocked), it seems bound to cause audio issues, so probably the only solution is to run in High Performance mode all the time and be more aggressive about putting the PC in standby to offset the increased power usage.

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  • 4 weeks later...

I've been having an issue for a while now with that something is constantly using 10-20% of my CPU, and it's only on the first core.  I've diagnosed that it's system interrupts and it seems to be ndis.sys and ataport.sys, but I can't figure out what's causing it.


Here's the .etl.


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ok,got it.


The IdePortInterrupt from ataport.sys is very high. This sounds like your HDD running in the old IDE mode instead of AHCI.


Try to change to AHCI:





Does this fixes it?

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