Interrupt affinity policies, latency spikes and weird behaviour

Discussion in 'Videocards - NVIDIA GeForce Drivers Section' started by klunka, Oct 16, 2020.

  1. EdKiefer

    EdKiefer Ancient Guru

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    IMO, I don't think it would matter but every system is different. The only thing I do is turn off power management in the device manager for USB devices.

    But if you have a problem, then try it and see if it improves.
     
  2. BlackNova92

    BlackNova92 Active Member

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    i'm actually curious about this, i've set my gpu to IRQ 16, i know there are several other values, but what exactly would a value of 16 do compared to one that is higher like 20-30?
     
  3. EdKiefer

    EdKiefer Ancient Guru

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    You would be better off setting GPU into MSI mode so no sharing with any other IRQ.
     
  4. mbk1969

    mbk1969 Ancient Guru

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    How exactly have you set GPU to IRQ 16?
     

  5. Smough

    Smough Master Guru

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    30 us isn't a latency spike at all. Anything below 150-200 is fine, below 100 is optimal, there will be spikes; even at idle to over 100 at times, it's normal, Windows is like this, it does background stuff so that leads to spikes sometimes. But it does not really affect games unless they were 1000us constant spikes. However, 30 us for USB seems a bit high, since on my 1809 Windows is only 5, spikes to 10-15 if I move the mouse very quickly, but nothing strange. Still, as I said, 30 is something you will never notice.

    You can get low latencies by disabling services, using MSI modes and using bcdedit tweaks, but I am still not sure if they are good for gaming, but 100% these 2 do lower DPC latency a bit more.

    Open CMD as admin and type in: (Press enter after doing each command).

    bcdedit /set useplatformtick yes

    bcdedit /set disabledynamictick yes

    Then reboot.

    To undo them, open CMD as admin again and type in:

    bcdedit /deletevalue useplatformtick

    bcdedit /deletevalue disabledynamictick


    And reboot.

    Try them and see if they make any difference, if they don't, return to stock settings.
     
    Last edited: Oct 19, 2020 at 1:20 AM
  6. mbk1969

    mbk1969 Ancient Guru

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    @Smough
    Check your post for typo :cool:
     
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  7. klunka

    klunka Member

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    I'm not looking for ways to lower my latencymon numbers. In the OP i already wrote how I can completely remove the spiking by changing GPU affinity mask.
    I want to figure out why this is happening....why is nvlddmkm not spreading DPCs, no matter the affinity mask or interrupt steering I set? Why is my usb driver affected by gpu affinity masks that seemingly make no difference?

    It's a long shot to ask. Probably noone here can recreate this issue which makes it even harder to find an answer. I appreciate the discussions anyway!
     
  8. BlackNova92

    BlackNova92 Active Member

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    sorry i'm stupid, i meant my system not gpu, i still had gpu in mind because of my issues with it. whoops.
     
  9. janos666

    janos666 Master Guru

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    The question remains (and only get wirder): How did you set your system IRQ to 16? (Hint: there is no such thing as system IRQ)
    Did you find some IRQ settings in your UEFI Setup?
     
  10. EdKiefer

    EdKiefer Ancient Guru

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    Hehe, that brings back memories with an old 440BX MB were you could set device IRQ so no sharing in OS, I think that was around the W95-98 timeline :)
    But yeah, there no "system" device, only the system process.
     

  11. janos666

    janos666 Master Guru

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    I can still set the IRQ of the serial port (SuperIO) on my Z370 board. And there is an option which controls some similar parameters (some resource allocation limit or such, I can't recall the name) which might be confused with IRQs by some at first glance (even though that's something else).
     
  12. BlackNova92

    BlackNova92 Active Member

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    i was talking about this thing here: "Win32PrioritySeparation"=dword:00000016
    it might be something completely different, i think IRQ8Priority set to enabled via reg.(i think i meant that), must have mixed things up on my end, sorry about that.
     
  13. mbk1969

    mbk1969 Ancient Guru

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    https://docs.microsoft.com/en-us/previous-versions//cc976120(v=technet.10)?redirectedfrom=MSDN

    https://medium.com/@dikrek/processo...ndows-and-a-bit-about-unix-linux-fb5ab02828e2

    I would suggest to you to not waste your time with this...

    PS And has nothing to do with interrupts.
     
    Last edited: Oct 19, 2020 at 8:27 PM
  14. BlackNova92

    BlackNova92 Active Member

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