Windows 8's greatest weakness: DPC latency

[geissler]

Windows 8 RTM, Enterprise N version, fresh install on a Lenovo T400 with no additional drivers. This is frankly unacceptable - I wanted to approach windows 8 with an open mind, and I applaud the new metro overhaul, but this makes any windows 8 machine completely useless for any kind of live or low latency audiovisual uses.

 

[Kristijonas]

Ouch... thanks for sharing this geissler. Let's wait and hope for an update for this from MS.

 

[xscess]

I've got similar result to "geissler" too... on a fresh installation of Windows 8 Pro RTM x64 with nVidia 304.79 beta drivers.

Here's the Youtube link for those interested:

 

[ViRGE]

Make sure you guys are running the Windows Performance Recorder. Since we have MS paying attention to this thread, that's the telemetry data they need. Just posting DPC results won't be particularly useful.

 

[Kristijonas]

Make sure you guys are running the Windows Performance Recorder. Since we have MS paying attention to this thread, that's the telemetry data they need. Just posting DPC results won't be particularly useful.

What is that and where can it be found?

 

[xscess]

Make sure you guys are running the Windows Performance Recorder.

In Windows 8 Pro x64, by the search term "Performance" I couldn't find "Recorder" but I did find "Performance Monitor".

New Youtube link with Performance Monitor in the video capture.

Here are the screens to get to the Performance Monitor:

 

[ViRGE]

You need to install it from the Windows 8 SDK. It doesn't come with Windows 8.

http://blogs.technet.com/b/home_is_...stall-the-windows-8-performance-recorder.aspx

 

[xscess]

@ StokesMSFT

As suggested by ViRGE, I've installed the Windows 8 SDK, and performed two tests while running Windows Performance Recorder on a fresh installation of Windows 8 Pro RTM x64.

The tests have generated 1.79 and 1.92 GB .etl(Windows performance analyzer trace file) files. Let me know where to uploads these files via PM. Thanks alot.

Edit: There's a program/plugin named "GPU View" was installed along with Windows 8 SDK, which can view that .etl file. This is how it looks like(Youtube link).

 

[StokesMSFT]

Hi folks, can a mod lift my ban on PM'ing individuals so I can get this trace file info from xscess?

Thanks much,
Jeff

@ StokesMSFT

As suggested by ViRGE, I've installed the Windows 8 SDK, and performed two tests while running Windows Performance Recorder on a fresh installation of Windows 8 Pro RTM x64.

The tests have generated 1.79 and 1.92 GB .etl(Windows performance analyzer trace file) files. Let me know where to uploads these files via PM. Thanks alot.

Edit: There's a program/plugin named "GPU View" was installed along with Windows 8 SDK, which can view that .etl file. This is how it looks like(Youtube link).

 

[StokesMSFT]

I should have posted instructions on how to collect the trace with WPR, my bad. Had a busy weekend

The WPR should have an "Audio Glitch" scenario capture profile in it. Just capture and then let it run and for say a minute and stop it.

Zip and PM me and we'll get in touch.

Thanks,
Jeff

 

[xscess]

hi Jeff

PM-ed you last night and just now... did you get any of the PM or not... let me know via PM/post, Thanks.

 

[StokesMSFT]

I did but I am a new member and not allowed to PM people until I post 10 times, doing that now, sorry to break forum rules :S

 

[hhhd1]

Postirini

Sounds like italian food.

@ the topic starter,

You can try to go to the device manager and disable all hardware there, and test again,

Disable everything you do not need to be able to run the tests.

 

[StokesMSFT]

I'm curious, if disabling all Network interfaces fixes this. Educated guess. I haven't seen anyone's traces but from my own machines (AMD FX 8120 and an Intel Core i7 2640m) and I think I might perceive a pattern in ETW analysis here. But I need more depth I think.

 

[StokesMSFT]

Well, tests on my machine say no that doesn't matter on DPC latency.

 

[xscess]

@ Jeff

Regarding disabling anything at all...

I mean if you don't disable anything in Win 7 then you shouldn't disable anything in Win 8 either, as you get DPC latencies between 40 to 160 μs in Windows 7(instead of ~1000 of Win 8), on the same hardware...

 

[StokesMSFT]

Yep. I'm looking at this but I think I'm seeing what is mentioned here in the forums on my hardware as well.

 

[StokesMSFT]

And yeah I hear what you are saying about how you shouldn't have to disable anything, totally agree, just troubleshooting at this point.

 

[StokesMSFT]

So I was reading one of the graphs wrong in WPA, the latency I see is max around 200us...Working with some folks internally to look at the trace submitted on this thread.

 

[lopri]

Same on my systems as well. I haven't tried anything DPC-sensitive yet, however.

 

[MrMuppet]

On Windows 7 I get an average DPC latency of 45 microseconds with periodic spikes of around 300, versus a constant ~1000 on Windows 8. It was very noticeable to me before investigating the issue, because I watch videos and play video games, which are very sensitive to latency. I could not enjoy any content because of the micro-stuttering, and no combination of driver has affected the latency for me.

That makes no sense. Audio popping and crackles? Yes. Video playback and video game micro-stuttering? No.

1 ms is nothing in terms of visual micro-stuttering. That's less than one eighth of a frame on a 120 Hz screen.

Stuttering audio on the other hand...

 

[lopri]

I've just did a quick test and it indeed drops A LOT of frames if a video clip is out of focus. (i.e., playing in the background of other windows or browsers) I presume the same is true for multitasking scenarios or networked environments. This is very troubling.

 

[MrMuppet]

I've just did a quick test and it indeed drops A LOT of frames if a video clip is out of focus. (i.e., playing in the background of other windows or browsers) I presume the same is true for multitasking scenarios or networked environments. This is very troubling.

Uh, that happens for me a lot in Windows 7.

 

[OneOfTheseDays]

Please people report this to MSFT.

This is a serious flaw and they will address it once the community sheds light on it.

 

[StokesMSFT]

My two systems ETL traces (these are authoritative traces to judge CPU usage/latency, etc) and the two I've had xscess upload do not reflect the same DPC latency as the tool that is being quoted on this forum. I can't address this more but have turned it over to folks that can. More info should be forthcoming. All I can say at this point.