4.3.0 massive DPC latency

[random717]

Hi

I'm getting massive DPC latency spikes causing audio issues and jerky mouse movements on the host, whenever there is high CPU usage on the guest.
Host is Win 8 64bit, on a DX58SO with an i7 950 and 6GB RAM, VTx enabled, and VMs running on a 2x500GB RAID 0 partition.
Virtualbox version 4.3 r89960
Guests are Windows 7 64bit, 32bit, Centos 64 bit, all running latest guest additions, using 2 cores with 90% cpu limit, 2GB RAM. I haven't run any of these simultaneously.

Using DPC Latency checker 1.3 (which is apparently inaccurate in Windows 8) I get 500us - 1000us with host and guest idle. Running a 7zip benchmark causes spikes up to 280000us...

Let me know if you need more info?

edit: just tested with 32bit Win 7 guest, with single core and VT-x disabled and had no spikes

[Martin]

What happens when you remove the CPU limit?

[jorgensen]

Interesting as I offload programs to VB guests to have lowest possible latency on the host for audio performance.
Checked it on my 'legacy' XP setup with version 4.2, and absolutely no problems here.
Obviously Win 8 has changed the hardware and software interface to be more compatible with tablets, and I would never use the current Win 8 version when low latency is crucial. Have experienced extensive hiccups when testing the Win 8.1 on the VB 4.3 version.

[random717]

What happens when you remove the CPU limit?

No difference.

Added a 3rd core and managed to hit 501145us during bootup of Win74 x64 guest. Not sure how accurate the numbers are, but the audio distortion is real, turns classical music into dubstep...

[Ramshankar]

turns classical music into dubstep...

Maybe we should have added that to our features list

More seriously though, this is a known VBox issue and we know where the problem is but we haven't got around to fixing yet.

[AndrewG]

I'm having the same problem. Win8x64 host. Win7x64 and Ubuntux64 guests. With vbox 4.3 any cpu/disk use on the guest seems to make host sound stutter. DPC latency checker, on the host, shows bursts of 160000us peak. Rolling vbox back to 4.2 fixed the issue. No more stuttering. DPS peaks are 4000us to 8000us.

[random717]

More seriously though, this is a known VBox issue and we know where the problem is but we haven't got around to fixing yet.

Is now a good time to say thanks for the awesome job you guys are doing! Keep up the good work! Where can we send chocolates to?

[frank]

Could you check if this build fixes the problem? Actually the problem is not really fixed but the build contains a workaround so any feedback is welcome. Thank you!

[AndrewG]

Could you check if this build fixes the problem? Actually the problem is not really fixed but the build contains a workaround so any feedback is welcome. Thank you!

That build does not fix the audio stuttering in the host. 4.3.2 also has the stuttering. The last release to work ok was 4.2.

[Kumba]

I noticed this as well when testing VBox 4.3 Beta1 to see how well NetWare 6.5 worked. Unfortunately, stuttering audio drives me bonkers, so I had to switch back (again) to 4.0.x so I can still toy around with NW and DOS. At least this time, there's an update to 4.0.x available. I'll keep tabs on this thread to see if/when this DPC thingy gets fixed.

[AndrewG]

Why don't you go to 4.2 instead of all the way back to 4.0?

[Kumba]

Why don't you go to 4.2 instead of all the way back to 4.0?

4.1 and 4.2 don't boot NetWare 6.5 (and earlier) at all, due to several issues, one of the big ones being that NW doesn't set the CR0.WP bit on the CPU. This can cause the 65SP8 install CD to throw a guru meditation. There are probably some other issues still left as well, as when I tested out 4.3.0 BETA1, and tried SMP, the server still ABENDs (NW's version of a BSOD or kernel panic). But that's probably SMP-related issues. When this stuttering problem gets fixed, I hope 4.3 will run NW6.5 in UP mode again, and maybe I can port my NW3.12 and NW4.2 guests back to VBox, too (they're currently on a super-old version of Qemu). That is all in addition to the two Windows Server guests, and two Linux guests I play with at times.

NW-related tickets I've opened:
https://www.virtualbox.org/ticket/9422 (closed/fixed)
https://www.virtualbox.org/ticket/10728 (open)
https://www.virtualbox.org/ticket/10729 (open)
https://www.virtualbox.org/ticket/10730 (fixed in SVN/open)

[michaln]

NW-related tickets I've opened:
https://www.virtualbox.org/ticket/9422 (closed/fixed)
https://www.virtualbox.org/ticket/10728 (open)
https://www.virtualbox.org/ticket/10729 (open)
https://www.virtualbox.org/ticket/10730 (fixed in SVN/open)

It would be good if you could update the open tickets for 4.3.x. I can more or less guarantee that there won't be any NetWare-related fixes in the older versions.

[Kumba]

It would be good if you could update the open tickets for 4.3.x. I can more or less guarantee that there won't be any NetWare-related fixes in the older versions.

Yeah, I know from Frank's statements that fixing NW support was too intrusive of a change for the older releases. It sounds like the DPC latency issue isn't though, and it might be fixed in an upcoming 4.3.x update. I tend to listen to music a lot when experimenting with these various guest OSes, so having my sound constantly skip is rather distracting, which is why I am still sticking w/ 4.0.x for now. I can probably try 4.3.2 out temporarily to check what configurations of my NW65SP8 guest OS boot and update the tickets, but that won't be for a few weekends at least.

[michaln]

Yeah, I know from Frank's statements that fixing NW support was too intrusive of a change for the older releases. It sounds like the DPC latency issue isn't though, and it might be fixed in an upcoming 4.3.x update.

Yes. And it has nothing to do with NetWare support...

I can probably try 4.3.2 out temporarily to check what configurations of my NW65SP8 guest OS boot and update the tickets, but that won't be for a few weekends at least.

Whenever you get around to it, it would be appreciated.

As for NetWare SMP, that's probably not going to happen. They're doing some very strange things. It's something that could probably be resolved if Novell was interested, but I suspect they couldn't care less.