Con Kolivas wrote:
On Friday 26 May 2006 14:20, Peter Williams wrote:
These patches implement CPU usage rate limits for tasks.
Nice :)
Thanks.
Although the rlimit mechanism already has a CPU usage limit (RLIMIT_CPU)
it is a total usage limit and therefore (to my mind) not very useful.
These patches provide an alternative whereby the (recent) average CPU
usage rate of a task can be limited to a (per task) specified proportion
of a single CPU's capacity. The limits are specified in parts per
thousand and come in two varieties -- hard and soft.
Why 1000?
Probably a hang over from a version where the units were proportion of a
whole machine. Percentage doesn't work very well if there are more than
1 CPU in that case (especially if there are more than 100 CPUs :-)).
But it's also useful to have the extra range if your trying to cap
processes (or users) from outside the scheduler using these primitives.
I doubt that degree of accuracy is possible in cpu accounting and
accuracy or even required. To me it would seem to make more sense to just be
a percentage.
It's not meant to imply accuracy :-). The main issue is avoiding
overflow when doing the multiplications during the comparisons.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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