DPC latency spike caused by two monitors

1 : Anonymous2021/10/25 09:08 ID: qfcn9y

Edit: I've found some more useful information. I decided to do a fresh install of win11 (previously was on win10) and noticed that when content isnt being displayed on the second screen, the DPC latency spike doesnt happen. Only when something like a browser, latencyMon itself or some other software is being displayed on the second screen, will the issue occur.

Edit2: Changing refresh rate to something like 60hz / 120hz doesnt solve the issue.

I've been able to finally deduce what was the issue plaguing me this whole time. For recap, previously I was experiencing random high latency spikes from the dxgkrnl.sys driver recorded by latencymon. It spiked into the 27ms randomly through a playthrough, causing visual stutter and audio stutter through my wireless usb dongle headphones. I tried everything from rebuilding my PC to reinstalling windows and disabling devices one by one, but only after disconnecting my second screen was I able to completely negate the latency spike.

It doenst matter into what display port I connect the screen, it always causes DPC latency spikes. I think this might be a driver issue and not one related to the card because of this. Is any of you guys experiencing this issue?

2 : Anonymous2021/10/25 11:00 ID: hhyzuy5

Interesting. What monitors are you running (refresh rate, res, adaptive sync? etc.). Is your GPU downclocking at all during gaming or do you have anything in the background that could cause this? (I know Discord was an issue for a while there with AMD cards).

ID: hhz7sr3

Discord is not installed. I'm running an LG 38gn950-b as my main screen and an Acer ED323QUR. The main screen is running with freesync on and I've tried 120hz to 160hz and nothing has worked. The second screen is running with freesync off and I've tried 60-75hz, again no change it the outcome. Depening on the game my GPU is downclocking, since its not being used 100%, while in others like cyberpunk it pegged at 2490-2550mhz drawing 305w. CPU hovers around 4.75-4.8ghz, with ram speeds of 3000mhz cl16 (I've ordered 2x16 3600 CL16 ram to replace those old ram stick I've been using since 2016-2017). I've installed win11 and the same issue is present here, though with less frequency.

Edit: Vermintide end times, Cyberpunk 2077 and witcher 3 are the games that exhibit this behaviour. Doom Eternal, Dyinglight and farcry 5 dont.

ID: hhzff3r

it's possible one of them is not using VESA standard timing..it's a trick some manufacturers do and use worse TCON's (LG i am looking at you f*ckers) to cheap out, however these causes issues like the famous VRAM staying always at max clocks. In many case it's not fixable as there will not be enough bandwidth supported to fit the signal with VESA timings even reduced ones. Thus you need to lower the refresh rate in order to fit it. Use CRU or custom resolution to try it and see if it fixes it

ID: hhzg0fr

I see, AMD GPU?

Try locking the core and see if you get the same issues. Last resort would to be disable free-sync / remove 2nd monitor.

3 : Anonymous2021/10/25 13:36 ID: hhzfber

Have you tried to run your system with only your secondary screen connected? If the issue is still present then it could be that monitor or the cable connecting it. Some AMD GPU's can have really strange issues with "bad" cables, so getting a good cable is recommendend (good does not mean expensive btw).

Level1techs on youtube released a really interesting video a few weeks ago, mainly on problems with flickering, but maybe it could help you:

ID: hhzg51f

I've been testing even more. It only happens when content is on the second screen. If the screen is empty, the dxgkrnl.sys driver never spikes that hard. I really think its a driver issue, since these cables have worked with vega 56, a 3070 and r9 fury.

ID: hi18byz

I have the same trouble and my friend too. Just a yt or twitch stream will trigger this issue. The moment the browser is open with or without hardware accelerated

4 : Anonymous2021/10/25 18:59 ID: hi0p8fk

I had a similar issue that was caused by Chrome with my 5700XT. No other browser showed the same symptoms, even other Chromium based browsers were fine, but Chrome kept nuking my frame times every 5-8s, even when just having a blank window with no extensions/add-ons running.

Was the final nail in the coffin for me, switched over again to Firefox as my main browser and never looked back.

ID: hi0urw6

For me the latency spike happens when something with GPU acceleration is running on the second screen. I currently use edge as a browser, it does a pretty good job.

5 : Anonymous2021/10/25 22:43 ID: hi1lqcs

Have you tried running them at the same refresh rate yet ?

ID: hi1mlmm

Havent yet, I'll do that tomorrow. That sad the only game currently where I cab reliably replicate it is vermintide end times, Cyberpunk and witcher 3 dont seem to show signs anymore.

6 : Anonymous2021/10/25 15:31 ID: hhzupjm

I have 4 1080p screens and have no high DPC latency.

X570E / 5900X / RTX 3090

ID: hhzxyjy

This seems to be then an amd related issue.

ID: hhzz3ml

Running triples with a 6900xt, no latency issues. All my screens are the same. Turning off freesync on the monitor fixes the VRAM clock speeds not down clocking.
Mixed refresh rate is probably the issue.

ID: hi05y1x

I just checked again and have huge latency spikes with the NV kernel.

My PC has been up for 3 days doing indexing. I'll restart later, re-test and report back.

ID: hi0q1jn

Drivers are often the #1 culprit in DPC latency issues so I wouldn't be shocked.

7 : Anonymous2021/10/25 09:11 ID: hhys6js

I'm running 4 screens, 2 4k, 1 1440 and one 3840x1200 and never noticed any difference in gaming between all or one screen running. Not saying it doesn't happen but nothing I've been able to spot.

ID: hhysopu

Which GPU are you running, I currently have a 6900xt red devil ultimate.

ID: hhyt0xj

In that machine it's a 2080 super. run a red devil Vega 64 on my second machine and didn't notice the issue either.

引用元:https://www.reddit.com/r/Amd/comments/qfcn9y/dpc_latency_spike_caused_by_two_monitors/

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