[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/sched_credit: Use delay to control scheduling frequency
On Tue, 2011-12-20 at 09:07 +0000, Ian Campbell wrote: > > > +/* Scheduler generic parameters > > +*/ > > +extern int sched_ratelimit_us; > > If this is generic then it seems like xen/sched.h is the right place for > it. Yes, this should be declared in xen/include/xen/sched.h. > Is it really generic though if only the credit scheduler applies it? The concept is generic enough that I think saying, "This is the control, not all schedulers implement it" makes sense. credit2 *may* in the future have use for such a control; at which point it would be a bit asinine to have two switches, named "credit_sched_ratelimit_us" and "credit2_sched_ratelimit_us". > > + /* If we have schedule rate limiting enabled, check to see > > + * how long we've run for. */ > > + if ( !tasklet_work_scheduled > > + && sched_ratelimit_us > > + && vcpu_runnable(current) > > + && !is_idle_vcpu(current) > > + && runtime < MICROSECS(sched_ratelimit_us) ) > > + { > > + snext = scurr; > > + snext->start_time += now; > > + perfc_incr(delay_ms); > > + tslice = MICROSECS(sched_ratelimit_us); > > + ret.migrated = 0; > > + goto out; > > + } > > + else > > + { > > This is the same comment as the next block below, does it really apply > here too? > > Since the previous if block ends with a goto the else clause is a bit > redundant. Yeah, probably better w/o the else. > > +/* Default scheduling rate limit: 1ms > > + * It's not recommended to set this value bigger than > > "sched_credit_tslice_ms" > > + * otherwise, something weired may happen Hui, "something weird may happen" is fine for informal speech, but for comments we tend to use more formal language. I might say something like this: "The behavior when sched_ratelimit_us is greater than sched_credit_tslice_ms is undefined." -George _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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