Re: [REPORT] cfs-v4 vs sd-0.44

From: Rogan Dawes
Date: Tue Apr 24 2007 - 04:27:05 EST

Ingo Molnar wrote:
* Rogan Dawes <lists@xxxxxxxxxxxx> wrote:

if (p_to && p->wait_runtime > 0) {
p->wait_runtime >>= 1;
p_to->wait_runtime += p->wait_runtime;

the above is the basic expression of: "charge a positive bank balance".


[note, due to the nanoseconds unit there's no rounding loss to worry about.]
Surely if you divide 5 nanoseconds by 2, you'll get a rounding loss?

yes. But not that we'll only truly have to worry about that when we'll have context-switching performance in that range - currently it's at least 2-3 orders of magnitude above that. Microseconds seemed to me to be too coarse already, that's why i picked nanoseconds and 64-bit arithmetics for CFS.


I guess my point was if we somehow get to an odd number of nanoseconds, we'd end up with rounding errors. I'm not sure if your algorithm will ever allow that.

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