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

@mbk1969 in usbview i saw my companions ports, but i think i have one usb controller. here is my usb ports in device manager (view by connection):

so i think if i disable usb controller in bios i will lose all my usb ports, but how about disabling only usb3.1 ports( highlighted with blue color) trough device manager? is it good idea?

also i enabled msi mode on all device and rebooted, here is result:

did you have any further suggestion like changing SATA AHCI priority (because i install windows 10 and important programs on SATA SSD) or changing limit for some devices?

also someone in discord said me that "change NVMe to undefined because it can cause problems, so you should set all to undefined and enable msi mode"

 

No. Leave all USB ports as is. Just try to connect keyboard and mouse to USB2.0 ones without companions. When you connect USB device in port with companions it has to use port routing logic (in controller) and there should be no difference - USB2.0 or USB3.0 port it was.

You can set SATA AHCI controller to high priority - that is the default case for rigs without NVMe storage.

Usually you believe in default settings of device drivers for NVMe. And if you see real problems you can toy with settings (not because someone told you).

 

Wow, didn't think enabling MSI Mode would make such a difference! Wish I knew about this earlier.
Resizing windows now feels way more fluid and it feels like I just upgraded to a RTX 30 series card.

At first it didn't feel as smooth compared to emulated IRQ, but after setting my 2060S to "High" Priority, it was starting to feel better.
The biggest difference was setting my "Samsung NVM Express controller" from "High" to "Undefined" Priority and now games feel as smooth and responsive as games with Nvidia Reflex. No more microstutters too in games like CyberPunk.

After benchmarking, it doesn't seem like my 970 Evo Plus took a hit in performance but is there any reason why it is set to "High" priority by default?

 

By the will of its drivers developers.

 

I see. Are there any downsides to changing device priority?
What about reducing the "Limit" from 2048 to something more reasonable like 8 for the Samsung NVM Express controller? Since it uses 33 which is way more than the 8 threads I have in my system.

 

Only one - we are not sure how exactly that tweak works and how to measure its effect.

If NVMe controller utilizes multiple IRQs like network card - assigning each IRQ to separate CPU core and then servicing different network applications through separate IRQ - then it is logical to use as much IRQs as CPU cores in the system. But who knows whether this is the case... Fortunately there are benchmarks for storage devices, so you can experiment.

 

Funnily enough, lowering it down to just 1 IRQ doesn't seem to affect anything, all the benchmarks from CrystalDiskMark were within margin of error. Maybe a single consumer PCIe 3.0 NVMe drive isn't enough to saturate even one MSI? Perhaps the driver sets it to 33 just to activate MSI-X?

 

are there msi-x drivers? I thought msi-x not supports drivers yet

 

No.

No. Both MSI mode and MSI-X mode are ancient things - they were developed back in ancient PCI bus days.

 

https://www.igorslab.de/en/interrupt-problems-read-message-signaled-interrupts-msi/

 

they are a little late to the party like me "powersettingexplorer tool removes %5 percent lock" it translates I should try that too

 

There is error in article:

The whole thing does require reboot, so not "in real time".

 

Yup, while it updates the reg you do need to reboot so driver goes to MSI IRQ.

 

how do I reset the interrupt priority to default? I think even removing the device didn't restore it to default, I don't remember what was the priority for my Mellanox 4 LX network card and the Intel USB3 suppose to be undefined right?

 

"Undefined" will remove setting from registry and device drivers will use device`s default. There is another default value - what was specified in device drivers inf-file. So you can find device drivers inf-file and see there.

 

Are there any downsides to lowering the number of MSI?

 

Depends on usage pattern of multiple IRQs. For example, network cards can assign each IRQ to separate CPU core, and then each IRQ can be assigned to separate process (https://docs.microsoft.com/en-us/wi.../network/introduction-to-receive-side-scaling).
What NVMe or USB controllers do with multiple IRQs I do not know.
So to answer your question we have to know exact mechanics in device drivers.

 

out of curiosity I tried turning off msi for the onboard i225-v or not running it in msi mode
it bluescreens when loading windows with a reference pointer error and basically loops like that so you either go to an earlier restore point or disable the device in bios then boot and uninstall or reinstall drivers to correct it

more curious as to why it has to run in msi mode or is it just conflicting when running normal irq and I can never see that because it won't allow me to get all the way into windows

I doubt you can make the utility able to see disabled devices and their current setups in the registry when they are disabled so I guess any thoughts on the subject?

 

Shared IRQs should be handled by Windows. Strange BSODs considering that network card is not needed at boot stage.

I can do that, it just never occurred to me to be useful.

 

yeah I'm not entirely sure why it causes it but when I uncheck the box for the nic with the MSI_util_v3 and restart it goes into the bluescreen boot loop when it tries to load the windows login screen

I wonder if it's just not something supported for the i225 nic

oh, well that would be helpful to undo changes in some scenarios