DAX has very high CPU utilization

KD4UNX

Hey, all. I did some searches about this but seem to only find old posts.

After firmware version 4 came out, I upgraded my radio and Windows 10 laptop to the v4 firmware, but it never worked properly on my laptop, so I downgraded radio and SmartSDR to v3.10.15.

Ever since then, DAX takes 40-50% of CPU. I have worked with ChatGPT today for several hours, but I don't seem to be any closer to getting this resolved. I have uninstalled and reinstalled SmartSDR, the DAX drivers, the devices, and many other things countless times today.

I finally have SmartSDR taking only 5-10% of CPU, where it was taking 40-50% earlier.

Now, before I did the v4 upgrade, my Lenovo L470 worked fine. All I use it for is Winlink Wednesday, so I launch SmartSDR (+ DAX + CAT), then I launch Winlink Express. From there I launch Winlink Vara, which launches VARA HF. All of this worked before the v4 upgrade.

ChatGPT suspects that SmartSDR and DAX are not using the GPU (mine is an Intel 510), but I did confirm that SmartSDR is allowed to use the GPU in performance mode (not limited mode).

Anybody have any suggestions on what I should do here? I'm really a Unix & macOS guy, and only use this one Windows system for only this one purpose, and I really don't know where to go from here.

Thanks.

jim.n2gxj

I've found a work-around, without knowing the cause.
When you are using smartSDR and the total CPU usage in Windows for unknown reason runs away and goes up to 100% and stays there, start the task manager and sort by CPU utilization. If you're like me when get in this situation, will see that DAX and SmartSDR CAT have jumped up in utilization to where they are using as much CPU as SmartSDR, so that the three together are causing the CPU to stay pegged at 100%. This is not normal. And again, I am not sure the steps to get it to run away like this, but sometimes it does.
Have seen this with multiple software versions; downgrading hasn't avoided it (I've tried, sitting at 3.9.19 right now). Changing waterfall scrolling rates and things like that also are not the answer - because remember, normally the CPU is not pegged when using this software. It is just some condition that causes the DAX and CAT to run away from time to time.
When that happens, the work around I've been using is to right click in task manager on the DAX and the SmartSDR CAT, and "end task" for both of them, leaving just the SmartSDR from these three running. The CPU utilization goes back to normal range again, with SmartSDR alone still running. Then, start the SmartSDR CAT, and wait a few moments - it will re-appear in task manager but at a nice normal low percent CPU utilization and stay there (e.g. under 2%, which is more than an order of magnitude lower than when is in the runaway condition). Then start the DAX (if you need it), and it too will re-appear in task manager but at a nice low percent CPU utilization and stay there.
After doing the work-around, things are back to normal with SmartSDR doing its thing, along with WSJT-X, and all else running, with pleanty of CPU idle to spare.
Like you, I'd not seen it talked about much, or recently, but it just happened to me again tonight. First time in months.
Hope this helps,
Jim n2gxj

Mike-VA3MW

Jim

What are the specs on the CPU?

Do you have an external display card - this helps to off load the workload from the main processor.

It does sound like you are CPU bound and DAX is the one taking the hit. There are many things that can cause this that are part of the root cause that then impact DAX.

There are some tools that help to isolate this and you might want to look at LatencyMon

https://www.resplendence.com/latencymon

KD4UNX

Hey Jim. I tried all sorts of things and never did solve this on my laptop. However, I discovered that I have a Windows 10 VM on a Lenovo M900 (my VMware server), so I installed SmartSDR 4.1.5 on that, upgraded the radio, installed & configured VARA HF and Winlink Express, and was able to send messages with low CPU utilization for SSDR and DAX.

It all worked fine prior to the v4 upgrade, so it's too bad my laptop won't work for this anymore, but at least I have a working solution again. I'll probably just junk the laptop.

jim.n2gxj

Hi Mike-VA3MW,
what an honor! Your videos are legendary amongst us Flex users here in SNJ. Thank you.

>> What are the specs on the CPU?
>> external display card
>> LatencyMon
It's a Thinkpad, i5-5200U @ 2.2 Ghz. Intel 5500 graphics. And LatencyMod (thanks for that tip) is displaying conclusion system appears to be suitable for handling real-time audio and other tasks without dropouts.
And I'd agree.
To be clear, I can run SmartSDR+DAX+CAT with WSJT + Gridtracker concurrent, cpu/memory/io utilization showing no problems - almost every time I use the radio.
Almost all the time DAX utilization stays negligible (< 2%) when in use with FT8. I wish I knew how to trigger the runaway on demand, so I could share, but haven't figured it out yet. Is very rare, but once it happens, it does not self-correct and go back down again until I restart the DAX and CAT again.

Mike-VA3MW

GridTracker and WSJT are CPU intensive but you might be near the edge of the envelope. Can you move GridTracker to a difference computer?

GridTracker has to look through your 'log' everytime it decodes to see if you need the grid or country.

I guess I would see if you the problem goes away without using GridTracker as a test.

The other thing is that the CPU is being used to draw the screen, so these all add up. DAX takes the hit, or we can see it take the hit when you become CPU bound mostly because it is dealing with real time data.

Also, watch your DT times in WSJT. If they start to rise it is because the CPU is busy and it is taking WSJT longer to decode all the signals.

This could happen with all this going on and there there are a lot of WSJT signals to deal with in the passband.

Let me know if that helps a bit.

73, Mike