Messages in this thread | | | From | Con Kolivas <> | Subject | Re: scheduler interactivity - does this patch help? | Date | Tue, 10 Jun 2003 19:39:20 +1000 |
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On Tue, 10 Jun 2003 05:22, Felipe Alfaro Solana wrote: > On Mon, 2003-06-09 at 07:43, Martin J. Bligh wrote: > > I've had this patch (I think from Ingo) kicking around in -mjb > > for a while. I'm going to drop it unless someone thinks it's useful > > for some testcase you have ... anyone interested? > > > > Thanks, > > > > M. > > > > diff -urpN -X /home/fletch/.diff.exclude 400-reiserfs_dio/kernel/sched.c > > 420-sched_interactive/kernel/sched.c --- > > 400-reiserfs_dio/kernel/sched.c Fri May 30 19:26:34 2003 > > +++ 420-sched_interactive/kernel/sched.c Fri May 30 19:28:06 2003 > > @@ -89,6 +89,8 @@ int node_threshold = 125; > > #define STARVATION_LIMIT (starvation_limit) > > #define NODE_THRESHOLD (node_threshold) > > > > +#define TIMESLICE_GRANULARITY (HZ/20 ?: 1) > > + > > /* > > * If a task is 'interactive' then we reinsert it in the active > > * array after it has expired its current timeslice. (it will not > > @@ -1365,6 +1367,27 @@ void scheduler_tick(int user_ticks, int > > enqueue_task(p, rq->expired); > > } else > > enqueue_task(p, rq->active); > > + } else { > > + /* > > + * Prevent a too long timeslice allowing a task to monopolize > > + * the CPU. We do this by splitting up the timeslice into > > + * smaller pieces. > > + * > > + * Note: this does not mean the task's timeslices expire or > > + * get lost in any way, they just might be preempted by > > + * another task of equal priority. (one with higher > > + * priority would have preempted this task already.) We > > + * requeue this task to the end of the list on this priority > > + * level, which is in essence a round-robin of tasks with > > + * equal priority. > > + */ > > + if (!(p->time_slice % TIMESLICE_GRANULARITY) && > > + (p->array == rq->active)) { > > + dequeue_task(p, rq->active); > > + set_tsk_need_resched(p); > > + p->prio = effective_prio(p); > > + enqueue_task(p, rq->active); > > + } > > } > > out_unlock: > > spin_unlock(&rq->lock); > > I'm currently testing it on a modified 2.5.70-mm6 kernel (with HZ set to > 1000) and seems to help a little with XMMS's chunky audio playback when > X is reniced to -20.
I tried this patch way back when mingo first posted it and found it helped a little. Have a close look at it, though; all it does is limit max timeslice to 50ms when other tasks are running at the same priority. A better effect can and is obtained by changing max_timeslice to 50ms...
Con
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