Question Mouse and OS stutter from DPC Latency ?

[Saintj]

My PC has been suffering from some cursor hang ups/stutters when I restart or wake-up my PC. Also when I do things like open display settings and other things. I think I’ve narrowed it down to DPC latency issues. I’ve download latencymon and it’s coming back that the biggest spike culprit is CLASSPNP.SYS.

I can’t figure out what drivers this is referring to. I’ve done as much as I can. Updating BIOS, and all the subsequent drivers from Asus like chipset, MEUpdateTool, LAN/WIFI, Realtek audio, etc. Tried new and old Nvidia GPU drivers. I can’t seem to get rid of this OS stutter. I don’t know why it happens the most right after signing in at startup/waking from sleep. Is that just common windows behavior? I never used to have it happen.

 

[Colif]

Have you tried any of these??

What are specs of the PC?

 

[Saintj]

@Colif Yes I’ve tried the things in that video. I don’t know if DPC latency is the reason for my issue it’s just what I’m thinking at the moment. I only get the mouse hang ups/freezes at pretty specific times. On the Lock Screen when signing into windows (although it may just depend on how quickly I sign in, it may also happen very shortly after signing in, like within 15 seconds). Also after waking the PC from sleep when it went to sleep from being idle for too long. It also happens when I enter display settings, but ONLY the first time. It won’t do it again on display settings again until the PC is restarted/woke from sleep.

I also kept latencymon running when I put it manually to sleep to test the readings. When I woke the PC there was a spike from ntoskrnl.exe. Along with the occasional spike from CLASSPNP.SYS mentioned earlier. I should note that I wasn’t seeing this issue when I would uninstall my Nvidia GPU drivers and just boot with no display driver. That seems like it’s related somehow.

i9 9900k
RTX 3090
32gb Corsair vengeance ram 3200hz using XMP 1
Asus Maximus XI hero WiFi motherboard (recently updated the BIOS so I went to Asus download center and installed everything on the motherboards page)

 

[Colif]

classpnp.sys is mostly USB items from memory.

So what mice/keybaords/Network cards do you have?

wait, me from a year ago said

classpnp.sys - scsi class system driver
normally runs alongside storport.sys to run your storage drives

[SOLVED] - DPC latency from classpnp.sys

I could hear light crackling noise from my PC so i decided to run dpc latency checker and the graph showed everything to be yellow and it said there's nothing wrong with my system, then I installed latencymon and it said classpnp.sys is causing the issue. Can any windows 10 masters help me fix...

forums.tomshardware.com

so what boot drive do you have?

 

[Saintj]

classpnp.sys is mostly USB items from memory.

So what mice/keybaords/Network cards do you have?

I’m using a razer mouse but have tried other brands and still have the issue. SteelSeries apex pro keyboard, I also have a yeti microphone plugged in, SteelSeries headset, and a pretty old Realtek speaker system as well (but it’s always worked). I don’t know about a network card, I just know I installed the most recent LAN driver from the Asus download page of my motherboard.

Never had this issue with these same peripherals for years until recently, maybe in line with when I updated the BIOS, but not certain.

 

[Colif]

i was wrong, classpnp.sys is a storage driver, normally used alongside storport.sys. Possibly for an nvme drive.

If you have a samsung drive, they have their own driver that can replace it.
who makes your boot drive?

can also be used for USB drives.

 

[kerberos_20]

I also kept latencymon running when I put it manually to sleep to test the readings

you cant use those readings lol, ofc ull get high spikes, pc was waking up

as latencymon doesnt really tell whats happening, you will need to use alternative tool, like windows performance recorder, there you can see what exactly is happening
https://learn.microsoft.com/en-us/windows-hardware/test/wpt/windows-performance-recorder

 

[Saintj]

i was wrong, classpnp.sys is a storage driver, normally used alongside storport.sys. Possibly for an nvme drive.

If you have a samsung drive, they have their own driver that can replace it.
who makes your boot drive?

can also be used for USB drives.

I use 3 Samsung SSD’s two are evo 870s 25gb and 1 tb. And my most recent purchase a 1tb evo 970 plus nvme m.2. The OS is on the 25gb 870 SSD.

But again nothing ever gave me problems before so why would they now?

 

[Saintj]

you cant use those readings lol, ofc ull get high spikes, pc was waking up

as latencymon doesnt really tell whats happening, you will need to use alternative tool, like windows performance recorder, there you can see what exactly is happening
https://learn.microsoft.com/en-us/windows-hardware/test/wpt/windows-performance-recorder

I thought that may be the case for that reading, thanks. Any other ideas as to what causes those mouse stutters after restarting and signing in?

 

[Saintj]

@Colif installed Samsung magician and have all the updated firmwares for my SSDs. Also installed the nvme driver listed on the Samsung website. The issue remains.

 

[Colif]

a pretty old Realtek speaker system as well (but it’s always worked).

Just because it always worked before, doesn't make anything immune to breaking.

I had a set of Logitech 5.1 speakers that always worked until they didn't. They started to not respond to the PC at start up and cause PC to not load desktop at all. That took months to figure out. As like you, I didn't suspect them. I was sad when I found out I had to replace them. They were part of the furniture. On my last PC, the only parts that caused any problems were peripherals.

Not saying they are cause but you can't ignore parts just because they always worked up until now. I would try unplugging things and see if it makes any difference to reaction. If they not plugged in, and it still happens, they aren't the cause.

 

[Saintj]

Just because it always worked before, doesn't make anything immune to breaking.

I had a set of Logitech 5.1 speakers that always worked until they didn't. They started to not respond to the PC at start up and cause PC to not load desktop at all. That took months to figure out. As like you, I didn't suspect them. I was sad when I found out I had to replace them. They were part of the furniture. On my last PC, the only parts that caused any problems were peripherals.

Not saying they are cause but you can't ignore parts just because they always worked up until now. I would try unplugging things and see if it makes any difference to reaction. If they not plugged in, and it still happens, they aren't the cause.

Unplugged the speakers and mic so it was only keyboard and mouse, issue remains. I wonder if this is just normal windows behavior right now? Is the OS loading some kind of driver and everyone gets this? It only happens once within 10 seconds of signing into windows, and once when I open display settings. It doesn’t seem to happen again until the PC is restarted or woken from idle sleep.

edit: also just happened while checking for windows update