Windows performance analyser, CPU usage attributed vs precise

I understand that this thread is old, but I have more information regarding DPC event durations and impact on audio:

I have discovered that there are DPC execution time events occurring every 15 minutes. There are two consecutive spikes of slightly varying duration that appear to be related to the number of cores, and when these spikes occur, it impacts ALL CPU cores for the duration.

I have had some issues with WPA trying to analyze sufficient data. However on rare occasions I am able to collect and report up to one hour. Most of the time, not even close to one hour. It amount to around 17GB of data, so not entirely surprising.

At any rate, these longer duration captures make it easy to see the DPC execution spikes and that when they occur ALL cores are pegged at 100% during the event.

While this is a Windows 10 forum, I can also say that these spikes also occur in Windows 11.

What I have determined is that these spikes are NOT random! What is random is what the system is doing at the time they occur that causes variations in the duration, sometimes triggering latencymon to indicate not suitable for real-time audio. Again, the situation is worse in Windows 11.

I've been experimenting with Process Lasso to try to mitigate the issues, but so far have been unsuccessful in determining the root cause or a reliable "fix". It doesn't help that MPA has trouble with this much data, nor that I'm pretty new to using the tool.

I continue to investigate but am not sure yet what is happening, nor how to determine the cause. Someone should know what is happening every 15 minutes in Windows that could cause this. So far, no luck isolating.

I have a new build with dual-boot Windows 10 and 11, and have verified that the DPC spikes occur on BOTH, with Windows 11 being more impacted.

Any pointer on how to better capture and interpret what WPA is indicating would be quite helpful! I can provide some data if needed, or try suggestions (within reason). I am actively experimenting with Process Lasso to try to isolate and potentially mitigate the ROOT CAUSE.

Thanks!

Hi David,
Good to see that someone took up the thread, I think there is interesting things to learn here for the audio people. I kind of understood that most DAWs will have a heavy load on the first processor and will not distribute 1 vst over multiple cores. I' ve the impression that it helps to make a vst like Kontakt use multiple processors, so you get a more even load.
Unfortunately I cannot help you with your question, but you might try at the cantabile forum where there is a bunch of very knowledgible people who certainly be interested.
Cheers, joop

Joop said:

Hi David,
Good to see that someone took up the thread, I think there is interesting things to learn here for the audio people. I kind of understood that most DAWs will have a heavy load on the first processor and will not distribute 1 vst over multiple cores. I' ve the impression that it helps to make a vst like Kontakt use multiple processors, so you get a more even load.
Unfortunately I cannot help you with your question, but you might try at the cantabile forum where there is a bunch of very knowledgible people who certainly be interested.
Cheers, joop

It is possible for the Windows scheduler to move tasks between cores, however as you suggest it cannot "distribute" the processing of a VST not written to handle multiple processes. Beyond that, a single-threaded VST would also be reliant on the tasking model of the VST host. For example, if each channel of a DAW were handled as a separate task/process and each channel uses an instance of a VST, there would be independent execution of the VST. However, if the VST itself is single-threaded, it cannot make use of parallel processing within its code.

I think it would be safe to say that a VST should be reentrant (i.e. callable by multiple tasks), it is not safe to assume that individual instances can be spread across cores if it is not multi-processing aware.

Hope that makes some sense.

In case you are interested
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