NVIDIA Release 368.95 Hotfix Driver for DPC Latency

Subject: Graphics Cards | July 22, 2016 - 05:51 PM |
Tagged: pascal, nvidia, graphics drivers

Turns out the Pascal-based GPUs suffered from DPC latency issues, and there's been an ongoing discussion about it for a little over a month. This is not an area that I know a lot about, but it's a system that schedules workloads by priority, which provides regular windows of time for sound and video devices to update. It can be stalled by long-running driver code, though, which could manifest as stutter, audio hitches, and other performance issues. With a 10-series GeForce device installed, users have reported that this latency increases about 10-20x, from ~20us to ~300-400us. This can increase to 1000us or more under load. (8333us is ~1 whole frame at 120FPS.)

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NVIDIA has acknowledged the issue and, just yesterday, released an optional hotfix. Upon installing the driver, while it could just be psychosomatic, the system felt a lot more responsive. I ran LatencyMon (DPCLat isn't compatible with Windows 8.x or Windows 10) before and after, and the latency measurement did drop significantly. It was consistently the largest source of latency, spiking in the thousands of microseconds, before the update. After the update, it was hidden by other drivers for the first night, although today it seems to have a few spikes again. That said, Microsoft's networking driver is also spiking in the ~200-300us range, so a good portion of it might be the sad state of my current OS install. I've been meaning to do a good system wipe for a while...

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Measurement taken after the hotfix, while running Spotify.
That said, my computer's a mess right now.

That said, some of the post-hotfix driver spikes are reaching ~570us (mostly when I play music on Spotify through my Blue Yeti Pro). Also, Photoshop CC 2015 started complaining about graphics acceleration issues after installing the hotfix, so only install it if you're experiencing problems. About the latency, if it's not just my machine, NVIDIA might still have some work to do.

It does feel a lot better, though.

Source: NVIDIA

July 22, 2016 | 06:30 PM - Posted by Anonymous (not verified)

If you are having issues it is likely you are a SLI user, which NVidia have said is not fixed yet.

July 22, 2016 | 09:08 PM - Posted by Scott Michaud

Nope. I do have a GTX 670 hanging around doing CUDA, but only one GPU is assigned to graphics. (I only bought a single GTX 1080.)

July 22, 2016 | 06:44 PM - Posted by Anonymous (not verified)

Hey Scott,

Just in case you are interested, ALT+0181 gives you the "micro u" symbol - µ

ALT+248 gives you degrees - °

Sorry, I'm basically a fountain of almost-useless knowledge. Also, I type both of those symbols a LOT in my job. lol

July 22, 2016 | 09:10 PM - Posted by Scott Michaud

Heh yeah. I do èéê a lot, too.

July 23, 2016 | 05:05 AM - Posted by JohnGR

almost-useless knowledge

(ALT+0181) "μ" is the equivalent Greek letter for m.

At least now I know why people write uTorrent instead of mTorrent when they don't write μTorrent :D

July 23, 2016 | 06:38 AM - Posted by Jann5s

the translation to m is not useful here since it would create ms, which is mili-seconds not micro-seconds. using the u for micro is highly common and perfectly acceptable for me. Everybody understood what he was saying, right?

July 24, 2016 | 03:43 PM - Posted by Anonymous (not verified)

I feel pretty confident that everybody understood what he was saying. I honestly wasn't trying to imply otherwise; I just wanted to share a small bit of geeky knowledge in good fun. And I think John was responding in kind. We weren't trying to correct anything, just talking a little about the character and its use.

We're all good. :)

July 24, 2016 | 03:37 PM - Posted by Anonymous (not verified)

Yeah I was pretty sure it had an actual name and not "the micro u thingy," I just had no idea what it was, lol. I know what it (usually) means when I see it used (micro) and I know that in American English it gets replaced with a "u" frequently as shorthand when being typed on a keyboard that doesn't come equipped with µ normally. So knowing that, I figured "micro u symbol" would probably sufficiently describe it.

When I first started at my job, so many of the document templates used "u" for micro. I've spent a lot of time over the years correcting documents and templates to replace every instance of u with µ. Also changing every instance of, say, "210C" with "210°C". Many, many, many of these templates were first created by two guys, one of whom is The Owner, neither of whom knows about ALT codes or the Character Map, and neither of whom cares.

July 23, 2016 | 11:55 AM - Posted by Anonymous (not verified)

"ALT+248 gives you degrees - °"

Damnit, all these years I've been using ALT+0176 for °! All those wasted keystrokes...

July 24, 2016 | 03:44 PM - Posted by Anonymous (not verified)

I know, I used to use ALT+0176 too. The day I discovered ALT+248 was the day my life changed for the better. lol

July 22, 2016 | 07:32 PM - Posted by TekWarfare (not verified)

How does the music sound through your Blue Yeti Pro? :P

July 22, 2016 | 09:07 PM - Posted by Scott Michaud

Pretty good. It's a decent, 48kHz, USB sound card.

July 22, 2016 | 11:17 PM - Posted by quest4glory

Funny thing about DPC latency...pretty much nobody knew what it was until they were told to check for the problem...and then suddenly everyone was an expert on DPC latency (judging by the popular enthusiast forums.) Ask half of them what DPC is (still,) they couldn't tell you, but they know it's not good to have latency. Anyway, I'm glad they're fixing it.

July 22, 2016 | 11:29 PM - Posted by arbiter

Its kinda like gtx970, no one really noticed anything til 1 person checked and found it and made a firestorm.

July 23, 2016 | 04:29 AM - Posted by JohnGR

If GTX 970 had the specs that Nvidia was saying, it would have been closer to GTX 980. But owners will never find out about that. So, if you never learn what you lost, why be upset about it? Right?

On the other hand those 3.5GBs could be the reason for GTX 970 cheating in Doom, or if you prefer, using lowest settings to boost it's frame rate.
https://www.youtube.com/watch?v=FVb25eomcrI

July 23, 2016 | 06:20 PM - Posted by Anonymous (not verified)

These kind of things are just one of the reasons I will no longer buy Nvidia cards. Its its not inferior image quality its the planned obsolescence by way of their unified driver.

July 24, 2016 | 01:07 AM - Posted by Scott Michaud

Yeah, these sorts of things are done in drivers all the time. Actually, NVIDIA's tweaks made Brother's In Arms run worse, leading to Gearbox developers recommending users rename the executable.

It's possible that these tricks could mess with image quality in ways that users cannot easily circumvent, though. When a whole shader is replaced, it should theoretically look the same, but does it? When a texture causes a bad performance hitch in predictable scenes, is it acceptable for a driver to mess with it / stream in a lower quality until the full one is loaded / whatever?

Hard questions to answer, especially when, in DOOM's case, it allegedly affects measurable image quality. Was going to write a post on it, even was freshening up on the kinds of tweaks that driver developers do, but kind of blew my budget of time on the Async Compute editorial.

July 24, 2016 | 07:12 PM - Posted by Allyn Malventano

In the video you linked, the guy was switching from a 480 to a 970 on the same machine (same OS), then running Doom, and seeing odd issues. We keep two separate OS install SSDs for testing AMD / NV because of possible oddball issues like this.

July 23, 2016 | 02:03 PM - Posted by Anonymous (not verified)

A business' biggest dream. Sucker for customers who keep coming back for more even after being deceived. Reminds me of Apple fans.

July 22, 2016 | 11:33 PM - Posted by Scott Michaud

Heh. I hope I set reasonable expectations about my knowledge of it.

July 23, 2016 | 01:16 AM - Posted by Anonymous (not verified)

Its mindset. Nvidia and its faithful have always pointed to something other then itself to be at fault.

They reduced it.

July 23, 2016 | 04:53 AM - Posted by Anonymous (not verified)

It's been in anandtech reviews of motherboards for as long as I can remember.

August 19, 2016 | 07:31 PM - Posted by Oneduality (not verified)

The reason I dug into the DPC latency issue is that when it starts kicking in my fans spin up to high speed and my youtube videos glitch a bit.. the tools I have point to nvidia drivers..

I'm using the absolute latest drivers on my GTX 660 and it still crops up daily.. once it starts it doesn't stop until I reboot.. it's doing it NOW and I've not even played a single game or done anything taxing.. I have 32GB of ram, an 8 core 3.2ghz machine

It's annoying because it causes the fans to spin up, it causes weird video/audio issues randomly and it causes the whole system to run an elevated temperatures... From what I've read online, this has been an ongoing issue for many over the last couple of years..

By the way, I've updated every major driver.. sound, network, motherboard.. etc

July 22, 2016 | 11:45 PM - Posted by Edwin Liew (not verified)

This has happened to me ever since i got my new 1070, tried everything, powermizer, forcing p-state, tried every driver since. old card(660) no problems, this one? constant nvddlkm.sys spikes and freezes every 30s or so so much that I cant play at all.

July 23, 2016 | 04:08 AM - Posted by Ha-Nocri (not verified)

Did PCPer have an article about the issue before it was "fixed"? Can't find it.

July 23, 2016 | 05:09 AM - Posted by Anonymous (not verified)

Alert! Alert!

Found the AMD user.

July 23, 2016 | 09:32 AM - Posted by A (not verified)

Yes another fucking amd fanboy. Piss off.

July 23, 2016 | 04:08 PM - Posted by pdjblum

Neither did I. Guess they were too busy trying to fuck over AMD after Raja had the class and humility to come to fucking Kentucky.

July 23, 2016 | 05:40 PM - Posted by Anonymous (not verified)

Alert! Alert!

Found another AMD user. This one is possibly gay as well.

July 23, 2016 | 05:54 PM - Posted by Scott Michaud

Not appropriate.

July 23, 2016 | 06:15 PM - Posted by Anonymous (not verified)

You're right. I take it back and apologise.

July 23, 2016 | 06:04 PM - Posted by Scott Michaud

It's highly ineffective to try and convince someone that they're consciously and intentionally doing something. Again, if you see an issue, drop us an email.

If we fail to cover something, it's often because we don't know about it, or we didn't take it seriously at a glance. Sending us an email should put it on our radar.

July 23, 2016 | 07:55 PM - Posted by Tim (not verified)

This. Scott's article was the first I've heard about this issue. Our emails are available in our profile pages.

July 24, 2016 | 12:55 AM - Posted by pdjblum

This has nothing to do with the news posts or you or Scott or Jeremy. It has to do with Ryan and now Allyn. I believe it is reasonable and fair to call them out for what they write or say in a podcast or product video. Plenty of readers who disagree with me will let me know, sometimes without resorting to personal attacks. Not to say suggesting I am gay is a personal attack. I am pretty sure I am not and I will not use having a kid and a wife as proof as I know gay guys with female wife's and kids. Anyway, thanks Scott for sharing your knowledge and insight into many complicated subjects in the tech world.

July 24, 2016 | 07:05 PM - Posted by Allyn Malventano

I don't follow. You want me and/or Ryan to be called out about something we weren't aware of? It's not like people were emailing me about this and I blew them off. It's actually very rare that I get any emails about GPU / display related stuff, so when people try to call us out for not reporting on x or y, all I do is chuckle.

July 24, 2016 | 07:18 PM - Posted by Allyn Malventano

You guys really have no grasp on our relations with the companies whose products we review. When we find issues we report them, help the company replicate the issue, and retest and publish on whatever fixes they make. We are typically talking to the company *long before* anything goes live on the site.

Nobody at AMD feels like we screwed them over. Why do *you* feel that way? Or did we just hurt your feelings by tarnishing your favorite things with a legitimate issue?

July 24, 2016 | 07:41 PM - Posted by pdjblum

As long as no one at AMD feels you handled the issue in an unfair manner, I apologize for being a dick. I have to admit I have been buying the stock since June of 2015, so I am definitely sensitive and biased.

July 23, 2016 | 05:55 PM - Posted by Scott Michaud

I'm pretty sure we didn't.

July 23, 2016 | 04:53 AM - Posted by Anonymous (not verified)

Waaay to many hotfixes being released nvidia really needs to take step back and redesign their drivers

July 23, 2016 | 02:42 PM - Posted by anon (not verified)

Switched from my 290 to a 1070 hoping for a better experience in games like witcher 3 and sadly was extremely disappointed due to the massive spikes.

July 23, 2016 | 06:38 PM - Posted by Anonymous (not verified)

Wonder if this "fix" affected the benchmarks any. Seems pretty peculiar.

July 25, 2016 | 07:49 AM - Posted by Harney :) (not verified)

Thx for the write up glad where getting some news awareness out there

July 27, 2016 | 11:55 AM - Posted by Notional (not verified)

LatencyMon v6.50 supports Windows 10. At least that is what the dev claims: http://www.resplendence.com/latencymon

July 30, 2016 | 01:21 PM - Posted by genBTC (not verified)

yes. he said the other tool DPCLat does not, thats why he ran the Respledence LatencyMon

August 8, 2016 | 12:58 PM - Posted by haiu2323 (not verified)

I believe the driver issue goes down to the Maxwell-based GPUs as well. I have the 970 FTW+ edition and have experienced these audio stutters/hiccups whenever the computer stays on for a long time (the first 24-36hrs are usually stutter-free). When I run LatencyMon, the drivers that cause the spikes are usually the graphics card driver or the usb wifi adapter driver. I have since ruled out the wifi adapter since I tried to go back to the onboard wireless adapter and the audio stutters still happen.

August 16, 2016 | 07:20 AM - Posted by Anonymous (not verified)

Latencymon showed problems in Windows 8, and nothing I could do seemed to fix it including a clean install of W8. Problem manifested as CRACKLING AUDIO.

I upgraded the system to Windows 10 and it was fine.

Latencymon (v6.50) site: http://www.resplendence.com/main

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