Srivatsa Vaddagiri wrote:
On Thu, May 03, 2007 at 10:50:15AM +0200, Ingo Molnar wrote:
- EEVDF concentrates on real-time (SCHED_RR-alike) workloads where they
know the length of work units
This is what I was thinking when I wrote earlier that EEVDF expects each
task will specify "length of each new request"
(http://lkml.org/lkml/2007/5/2/339).
This is not very true based on my understanding of EEVDF, please look at
the email I just sent out to Ingo for explanation.
The other observation that I have of EEVDF is that it tries to be fair
in the virtual time scale (each client will get 'wi' real units in 1
virtual unit), whereas sometimes fairness in real-time scale also
matters?
For ex: a multi-media app would call scheduler fair to it, it it recvs
atleast 1 ms cpu time every 10 *real* milleseconds (frame-time). A rogue
user (or workload) that does a fork bomb may skew this fairness for that
multi-media app in real-time scale under EEVDF?
First of all, CFS does not seems to address this issue to. This is a
typical real-time or soft real-time question, that is not only the
bandwidth of a task has to be fixed, i.e. 10% of cpu bandwidth (which
proportional shared system, like CFS, EEVDF does not do), and the work
need to satisfy a deadline.
In both CFS, EEVDF, the scheduler have keep tweaking weights to give a
fixed bandwidth to application. Authors of EEVDF claims this can be
done, but never implemented :-(
Ting
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