Windows: Line-Based vs. Message Signaled-Based Interrupts. MSI tool.

Discussion in 'Operating Systems' started by mbk1969, May 7, 2013.

  1. BuildeR2

    BuildeR2 Ancient Guru

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    This is exactly why I systematically went through my UEFI/BIOS and disabled each and every USB port one by one until none of that was happening anymore. I'm still left with 6 of my 8 USB ports working just fine but none of the ISR or CPU time stuff.
     
  2. karaxx

    karaxx New Member

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    I am surprised, that it fixed the issue actually.
    I have no option in my bios to disable custom usb ports.
    I thought i would rather switch to ps/2 :D
     
  3. mbk1969

    mbk1969 Ancient Guru

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    ^ First Windows which supports MSI mode is Vista. I think that MS driver team just copied USB2 drivers from XP. But they couldn`t do that with USB3 drivers so they implemented MSI mode in them.
     
  4. karaxx

    karaxx New Member

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    Sad thing is, that USB 3 is generating ISR's too and has high Total execution time, even in MSI mode, at lest for me.
    But it doesn't when my mouse is idle, ISR's and DPC's both suddenly just stop.
     

  5. mbk1969

    mbk1969 Ancient Guru

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    ISR could not be ditched because it is how OS kernel reacts to devices activities. But ISR time can be decreased with help of MSI mode.

    As for idle devices - what is surprising you? When device has no activity it does not raise interrupts => hence no ISRs and DPCs.
     
  6. EdKiefer

    EdKiefer Ancient Guru

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    I wonder if polling/refresh rates on mouse have any affect on this.
    Many have options to 1k refresh but honestly I can't see a difference much above 125/250 or so, maybe if i had 144/166hz monitor i notice it.
     
  7. mbk1969

    mbk1969 Ancient Guru

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  8. EdKiefer

    EdKiefer Ancient Guru

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  9. karaxx

    karaxx New Member

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    Because on usb 2.0 it didn't work like that.
    USBPORT.sys was constantly generating ISR's and DPC's, even i didn't do anything with my mouse and keyboard and i wasn't using any other usb devices.
    And other devices like gpu for example, stop generating ISR's, after they are switched to MSI mode.
    So why should USB.
     
  10. tsubasa

    tsubasa New Member

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    How accurate is this information about the disadvantages of Message Signaled Interrupts and how much does this impact gaming and daily PC usage?

    I can't link the webpage where I found the information because this is a new account, however here is a quote.

    From what I understand MSI removes the latency caused by IRS routines or something along those lines but does the quote above mean that in reality it creates a new latency increase by making everything execute later in exchange making everything smoother?

    Arguably "many clock cycles" could still be only microseconds but is it enough to for example delay a video card by a frame? Or cause mouse input to be delayed?
     

  11. mbk1969

    mbk1969 Ancient Guru

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    I wonder what tools do you use to spy after ISRs and DPCs. LatencyMon?

    Unfortunately USB2 doesn`t utilize MSI mode. I don`t know what work usbport.sys does. It is listed along with usbehci.sys and usbhub.sys under the USB controller device. Ofc this activity you see proves that there are interrupts raised by some part of USB devices stack. May be it is caused by configuration of HW, FW and SW on your rig. Or may be it is supposed to be like that on every rig in any configuration.

    And once again (out of my pedantry) - MSI mode doesn`t stop ISR, because ISR is just routine in device driver called in response to interrupt from device, and interrupt is the only way for device to speak to CPU (to OS kernel).
     
  12. mbk1969

    mbk1969 Ancient Guru

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    Give the link to the article you quoted in dissected format - add some space chars or something.

    Update. I will quote Intel`s pdf document linked in OP:
     
    Last edited: Apr 3, 2017
  13. karaxx

    karaxx New Member

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    Yes latencymon.

    That makes sense, so than latencymon isn't showing ISR's at all, after switching devices to MSI mode, but they are still there.

    After switching graphic card to MSI, my total CPU execution time was approximately about 3000ms less for nvlddmkm.sys
    I tested it already multiple times at load, year ago.
    I could really tell the difference and input lag was much lower.
     
  14. mbk1969

    mbk1969 Ancient Guru

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    Only LatencyMon`s developers can answer to such questions. We can guess for example that program just ignores ISRs and DPCs execution times lower than some treshold value.
    Btw, you can check use another feature of LatencyMon - copy its report to clipboard (through menu item) and then paste it into notepad. There you will see amount of ISRs and DPCs executed on each core. May be that values will tell you whether amount has changed comparing to previous measurements.

    And another btw - total execution time is accumulated value which tells nothing about probable source of hiccups (or stutters) because if every IRS and DPC (of some device) were executed with minimum time then it should not cause troubles (theoretically speaking).
     
    Last edited: Apr 3, 2017
  15. karaxx

    karaxx New Member

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    I know it is accumulated time, but after switching to msi mode, it was nothing after a while in comparison to before, either gpu was idle, or in load.
    I measured it like 100 times and even in load after switching to msi mode it was lower, than before at idle :D

    It doesn't show difference in ISR's even in report.
     

  16. mbk1969

    mbk1969 Ancient Guru

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    Which is logical because MSI mode doesn`t cancel ISRs. Amount of ISRs should be the same but the time spent in ISRs should differ.

    But alas - not for USB2 which ignores the setting for MSI mode. I meant to use the text report of LatencyMon to compare cases with active USB devices and without - would the amount of ISRs differ?
     
    Last edited: Apr 3, 2017
  17. karaxx

    karaxx New Member

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    Ye it is does.


    For usb2, it is generating massively even when mouse and keyboard is not used.
     
  18. Blackfyre

    Blackfyre Maha Guru

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    This is not the case with my pascal card (MSI GTX 1070 Gaming X), I've tried everything and all the suggestions, but nvlddmkm.sys is always over 3000ms when I'm gaming. All other latencies drop, especially after switching all devices to MSI mode, and it helps definitely, but not the nVidia drivers. I think nVidia themselves have to fix the high latency issues with pascal.

    I want to do another clean install of Windows 10, but I am waiting for the final iteration of the Creator Update, and I'm waiting for nVidia to release WDDM2.2 drivers.

    I'm going to do a clean format, do Windows Update. Make sure all drivers are installed. Then install Latency Monitor, Origin, & Fifa 17 (the best game for spiking latency up for me). Might even take out the Soundcard and unplug every HDD except the SSD before formatting just to troubleshoot if any hardware is interfering somehow.
     
  19. lucidus

    lucidus Ancient Guru

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    With the CU I've noticed my realtek audio and nvidia hd audio are both MSI mode by default. Only the nvidia graphics driver is in the old mode (positive).
     
  20. Ferrouswogg

    Ferrouswogg New Member

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    I am wondering if must create a Dword and put this in??? MessageNumberLimit 0x00000001(1)????
     

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