Context Switching – The "hardware view"

I met George Dinwiddie so long ago, CompuServe ruled the online world. We participated in the Software Development Forum. He recently added to the context switching discussion. You can read George’s thoughts here. In it he states “This [hardware interrupt handling] is a very efficient and deterministic process. People, unfortunately, can have a little more trouble making such a context switch and then switching back.”

And Why is That?

People are incredible state machines. Our physiology and emotions create our states. We awaken in the morning and (eventually) go to bed, switching states all day long. Some states gradually morph into others. Some states grow stronger and allow us to get into flow situations where we enjoy the productivity of our thoughts and actions coming together creating high output levels. Some state changes happen abruptly when something jars us.

Restating George’s thought, it’s not the context switch out that’s difficult. It’s the context switch back. Unlike the wonderfully linear microprocessor, we humans tend to be incredibly nonlinear, tightly-coupled, loosely cohesioned (if you know what I mean) creations. This applies even to those of us who believe we are linear and straightforward.

The context switch destroys our current state. If the opportunity presents itself, we may have time to check point our thoughts and where we are in the process. But our thinking up to that point, our physiology, and emotions at that point get lost in the winds of change.

The return trip back then becomes a game of trying to find where we were, why we were there, and what we were doing.

I’m Disinclined to Agree

George stated this problem of people “switching and then switch back” is “unfortunate”. From a management standpoint, he may be correct. But managers would like to believe that knowledge workers are fungible, and that output equals the number of hours worked multiplied by some magic constant. That allows them to complete projects quicker by assigning more people, and having those people work more hours.

It just ain’t so. If you haven’t read Slack by Tom Demarco, do so. Order enough books so you get free shipping and give the extra copies to your manager, and his manager.

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