Commit 977dda7c authored Jan 14, 2011 by Paul Turner Committed by Ingo Molnar Jan 18, 2011

sched: Update effective_load() to use global share weights



Previously effective_load would approximate the global load weight present on
a group taking advantage of:

entity_weight = tg->shares ( lw / global_lw ), where entity_weight was provided
by tg_shares_up.

This worked (approximately) for an 'empty' (at tg level) cpu since we would
place boost load representative of what a newly woken task would receive.

However, now that load is instantaneously updated this assumption is no longer
true and the load calculation is rather incorrect in this case.

Fix this (and improve the general case) by re-writing effective_load to take
advantage of the new shares distribution code.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110115015817.069769529@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent c9b5f501

kernel/sched_fair.c

+16 −16

Original line number	Diff line number	Diff line
		@@ -1362,27 +1362,27 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
		return wl;

		for_each_sched_entity(se) {
		long S, rw, s, a, b;
		long lw, w;

		S = se->my_q->tg->shares;
		s = se->load.weight;
		rw = se->my_q->load.weight;
		tg = se->my_q->tg;
		w = se->my_q->load.weight;

		a = S*(rw + wl);
		b = Srw + swg;
		/* use this cpu's instantaneous contribution */
		lw = atomic_read(&tg->load_weight);
		lw -= se->my_q->load_contribution;
		lw += w + wg;

		wl = s*(a-b);
		wl += w;

		if (likely(b))
		wl /= b;
		if (lw > 0 && wl < lw)
		wl = (wl * tg->shares) / lw;
		else
		wl = tg->shares;

		/*
		* Assume the group is already running and will
		* thus already be accounted for in the weight.
		*
		* That is, moving shares between CPUs, does not
		* alter the group weight.
		*/
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
		wl = MIN_SHARES;
		wl -= se->load.weight;
		wg = 0;
		}

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