Re: Applications "buying" resources

On 30.12.2010 21:33, D Yuniskis wrote:
On 12/30/2010 6:47 AM, Hans-Bernhard Bröker wrote:
On 30.12.2010 09:53, D Yuniskis wrote:

First of all, note that a task can ignore ANY or ALL
of these "tactics"/requests (except, of course, the
last one :> )

That's exactly the problem. If they can, you have to assume they will.
Which renders the entire scheme moot.

By the same token, "voluntary multitasking" (each task
holding the CPU for as long as it wants before relinquishing
control to the next eligible task) "won't work". :>

And guess what: ultimately it doesn't. If that needed proving, experience with less-than-perfectly-behaved Windows 3.x programs has done just that to very convincing level.

This is fine in a closed-end, fixed functionality product. But,
if you open the product up to other applications, you run the
risk of those other applications misbehaving

Exactly. So if you want to guarantee any kind of real-time behaviour, you have no choice but to disallow such misbehaviour right at the source, i.e. foresee killing processes or threads (or at least taking the CPU away from them forcibly).

Once we agree you need to do that anyway, there's little, if anything, to be gained from offering other mechanisms on top of it. They only add complexity for little gain. You'll likely end up spending more effort in the kernel on getting all those niceties handled than it would have taken the application to just do the job at full throttle.
.

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