High CPU usage solved?

[gkreis]

This is presented in the hopes it might help someone else or give the ideas....

I had a problem of unhandled interrupts that flooded my setup causing very high CPU usage when a show was recording, though TaskManager showed very little CPU usage. Using the Process Explorer (from Systinternals.com - since bought by MS), I was able to find the out about the hardware interrupts and the DPCs that were eating the machine up.

I thought I solved it in this old thread (the thread subject in the hardware area is " Very high CPU usage with PVR-150 and GBPVR") and then the problem recently returned. I found that the AverMedia 150 tuner, the Dlink wireless card and the onboard audio were all sharing interrupt 11. That sounded bad. I installed a Soundblaster live 5.1 card that was laying around and as I disabled the onboard sound in the BIOS I noticed several other devices I could disable, freeing up interrupts! I turned off the serial ports, the parallel port, the onboard audio and game ports.

When I rebooted, each device (tuner, live! audio and wireless card) was on its own interrupt!! I never thought to disable the legacy ports to free them up.

For now, it appears the lost interrupts and DPC issues are gone. Now if they come back, I'll have to dig deeper and see if one of my cards is going flaky with intermittent failure. But it sure seems like a no-brainer, as I look back on it, to free up all those interrupts. (Who knows, maybe XP was handling the situation before just fine and it was a bad card, but it seems logical to hand out those unused interrupts.)

[gkreis]

Well, the DPCs are back while recording. So apparently there is a problem with the drivers or the card is bad.... sigh....

[SniperDude]

I was struggling with this for a logn time... and I found that everytime my cpu fan kicked on full blast.. the DPC's would be borrowing alot of cpu power.. causing issues with streaming, watching TV, and decoding video...

for me the solution was simple... I ran the program that came with the motherboard, called Cool and Quiet or something like that.. it basically allows for temp monitoring, and for monitoring speed of the fan, bus etc... anyhow.. the moment that program was running.... DPC's were gone.. litterally... I almost never see them taking more than 1-2% cpu vs (40-60%) and I am not having any trouble with overheating ... everything has been rock solid on this machine.. I rarely reboot it.. its on for months at a time.. current uptime.. 57 days... (Installed some new video drivers in beginning of Dec)

so perhaps that will help...

[gkreis]

That is interesting SniperDude. So are you thinking it was a hardware issue that surfaced when the heat was excessive or that something else messed up and the run away DPCs caused the CPU to heat, kicking in the fan?

My CPU never gets above 50C under load and typically is at 40-45C (I have an AMD Mobile XP processor installed and a Zalman copper flower style heatsink). I can't tell if this is a software problem or hardware or both. I've ordered a different tuner card, since the DPCs are happening when recording.

[SniperDude]

I dont know to be perfectly honest... yes my cpu never got hot to begin with either.. but the fan ran full speed pretty much all the time... til I started that little software... my guess its a chipset issue... but I do know... since I did that... I never see DPC's on my process mon for more than a few %, and very few seconds...

I run processmon (pretty much 100% of the time, so when I am watching something and it goes flukey, I can pull it up... and sigh a relief, oh yah its 11:00PM time for the EPG update )

[gkreis]

Oh... yes, a chipset issue! This could be related to the default software that XP installs instead of the drivers from the manufacturer. Good idea! I'll see if I can track down the latest chipset drivers....

[gkreis]

This thread shows how many people have DPC problems with drivers. These folks had problems with a Nvidia video chipset, but it is possible for any hardware and driver combination.

http://forum.sysinternals.com/forum_post...PN=1&TPN=1

Here are two tools from MS that you can use to monitor CPU use in the Kernel and lower. Neither one is a pretty GUI, but they will give you some idea which drivers, specifically, are eating up your CPU.

1. Google "Kernrate Viewer" for the download page a Microsoft.

2. http://www.microsoft.com/whdc/DevTools/tools/RATT.mspx

I am going to see what Kernrate shows. I used the RATT tool and I wasn't able to make sense of the numbers. Kernrate shows more promise from the previews I saw on the web.

[SniperDude]

nice find... will have to try it sometime myself...

[gkreis]

Well, KERNRATE was just what I needed! It immediately identified a driver for the Dlink wireless card that started eating up a bunch of the CPU whenever a recording started. That coincidence is why I suspected the tuner card! I pulled the wireless card and the CPU load went down to 3-5% while recording.

During playback of a movie I was seeing 65-85% CPU loads with frames dropping. After the wireless card was pulled, it went to 25-35% and was smooth again.

Apparently lots of activity on the PCI bus sent the wireless card and its driver into a flurry of activity. The wireless wasn't needed for these activities so I am not sure why it reacted that way.

What is also strange is that when I played movies with GBPVR as a client on a PC, pulling the movie from the PVR PC, it was smooth and trouble free. So the wireless card was working, but absorbing much of the PC at the driver interrupt level. Only something like media software that relies on reliable response time to avoid dropped frames would expose the situation.

I've read reviews from others on the Dlink card and they don't speak highly of it and I had a devil of a time getting it to work. I guess I'll see if another brand will work better.

[gkreis]

To wrap it up, I searched for a long time and finally found someone who had posted some reference drivers from the chip maker on the Dlink card (DWL-G520). They installed MUCH smoother than those from Dlink and the run away interrupts and DPCs appear to be gone. So it was a driver issue.

I am always amazed at how poorly the drivers works from hardware vendors. I guess it is really hard to write good Windows drivers. Maybe the blame sits on Windows? Anyway... when in doubt, hunt down some other drivers. Odds are that your hardware is fine.