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SubjectRe: Egg on my face -- disk speed
From
   Date: Wed, 4 Nov 1998 14:32:23 +0100
From: Pavel Machek <pavel@bug.ucw.cz>

> The only valid way to measure CPU utilization is to start a process
> which times how many interations of a busy loop can be executed per unit
> time while the system is quiscient, and then compare that with how many
> interations of the busy loop is executed while the disk copy (or serial
> transfer, or whatever) is taking place.

It might be nice for our idle process to burn idle cycles and compute
nuber of cycles burned. This would give pretty accurate numbers.

PS: I've done that. There is only one problem: it is _bad_ idea on
notebook computer. It may be even bad idea on desktop because more
power consumed means more heat and marginal hw will fail. (Not
counting adverse effects on environment...)

The way to handle this is to only have the idle process burn idle cycles
after a "start benchmark" system call, and then have it stop burning
idle cycles (and return the number burnt cycles :-) upon having received
a "end benchmark" system call.

Having such a feature (even if it were an optional kernel patch) would
make it a *lot* easier to benchmark device drivers for CPU efficiency.
(Hint, hint, to potential budding kernel programmers out there --- this
would be a pretty good beginning-to-intermediate kernel hacking project.)

- Ted

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