Jarek Poplawski wrote:
On 13-10-2007 03:29, Peter Williams wrote:
Jarek Poplawski wrote:
On 12-10-2007 00:23, Peter Williams wrote:
...
The reason I was going that route was for modularity (which helps
when adding plugsched patches). I'll submit a revised patch for
consideration.
...
IMHO, it looks like modularity could suck here:
+static unsigned int default_timeslice_fair(struct task_struct *p)
+{
+ return NS_TO_JIFFIES(sysctl_sched_min_granularity);
+}
If it's needed for outside and sched_fair will use something else
(to avoid double conversion) this could be misleading. Shouldn't
this be kind of private and return something usable for the class
mainly?
This is supplying data for a system call not something for internal use
by the class. As far as the sched_fair class is concerned this is just
a (necessary - because it's need by a system call) diversion.
So, now all is clear: this is the misleading case!
Why anything else than sched_fair should care about this?
sched_fair doesn't care so if nothing else does why do we even have
sys_sched_rr_get_interval()? Is this whole function an anachronism that
can be expunged? I'm assuming that the reason it exists is that there
are user space programs that use this system call. Am I correct in this
assumption? Personally, I can't think of anything it would be useful
for other than satisfying curiosity.
Since this is for some special aim (not default for most classes, at
least not for sched_fair) I'd suggest to change names:
default_timeslice_fair() and .default_timeslice to something like eg.:
rr_timeslice_fair() and .rr_timeslice or rr_interval_fair() and
.rr_interval (maybe with this "default" before_"rr_" if necessary).
On the other hand man (2) sched_rr_get_interval mentions that:
"The identified process should be running under the SCHED_RR
scheduling policy".
Also this place seems to say about something simpler:
http://www.gnu.org/software/libc/manual/html_node/Basic-Scheduling-Functions.html
So, I still doubt sched_fair's "notion" of timeslices should be
necessary here.
As do I. Even more so now that you've shown me the man page for
sched_rr_get_interval().
I'd suggest that we modify sched_rr_get_interval() to return -EINVAL
(with *interval set to zero) if the target task is not SCHED_RR. That
way we can save a lot of unnecessary code. I'll work on a patch.
Unless you want to do it?
Sorry for too harsh words.
I didn't consider them harsh.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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