This week: For no reason the high CPU utilization rate due to DPCs has gone. Again. A reader suspects Microsoft updates, and Microsoft’s Mark Russinovich suggests a diagnostic tool. Finally I recommend some OS X disk drive tools.
I don’t believe it! My problem with deferred procedure calls has again vanished and my PC’s CPU utilization has gone back to normal! Over the last few weeks DPCs in my Windows XP system have driven processor utilization from a normal 2% range up to 40%, basically killing the overall system performance. Then, after a few days it fell back to about 2%. I have watched my PC go through this cycle about three times.
I’m guessing that if Gearhead readers don’t have any insight on what is causing this then it must be something pretty obscure. I wonder if reader John Jobst (St. Louis) is on the right track: “Was your flummoxing rise then fall of DPC activity due to the installation of a driver that you didn’t know about? You’re aware, of course, that some Microsoft Update activity will take place whether you asked for it or not.”
Good point. John continued: “Perhaps Microsoft installed a buggy little something that was supposed to fix a buggy little something else, then retracted it a few days later? Rumor has it that this type of activity is still recorded in the logs, so it should be a straightforward search on the appropriate dates.”
Hummm … I looked in the logs but couldn’t find any clues. John also suggested that I see what Mark Russinovich had to suggest. He’s the author of the Process Explorer utility I’ve often mentioned in Gearhead and which was recently acquired by Microsoft. Good idea. I dropped Mark a note.
That was quick! Mark just replied and suggested I use the Kernrate sample profiling tool, which tracks how CPU time is spent for both kernel and user mode processes.
I had tried Kernrate back in the last bout of high DPCs, but I must have done something wrong because I couldn’t get any useful data out of it. Actually, if you look at the documentation for Kernrate, you’ll find that it is very complex and the instructions are poorly written, so it would seem likely that I just didn’t understand which of the gazillion options I should have been using.
What I need to do is find out how to configure Kernrate to specifically track which processes generate DPCs and then set up an alert in the Windows XP performance log and alert tool (under Computer Management under the Microsoft Management Console) to run Kernrate when DPCs exceed 10% utilization. More on this when I get it figured out.
So, what else is on my mind this week? Well, at the risk of losing my Windows audience, I have a couple of useful OS X disk tools (I hate the space between “OS” and “X” — it seems so out of place — it really should be something like “OSX.” Steve, you want to do something about that?).
First up is WhatSize from ID-Design, a free tool that shows you how space is used on your disk drives. WhatSize determines the size of all subfolders and files (including hidden and cache files) under a volume or folder and sorts what it finds by size. You can filter your view by size or type and delete as needed. Very useful.
My second tool addresses something that has bugged me since I got my Mac: No disk-drive activity light. Apple has eschewed such fripperies since the SE30, much to the irritation of people such as me. DiskSpy by Nick Zitzmann fixes this by adding a virtual disk-drive activity LED to the OS X menu bar. I am now a happy man. At least where drive lights are concerned. DPCs? Not so much.
