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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-06-27 13:41:32 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-27 14:31:43 +0200
commitcb5ef42a03a13f95a9ea94e6cda4f7a47497871f (patch)
tree4c94df72d2889ecce52bf74b141ae06d85d4708a /kernel/sched_fair.c
parent051c67640e771fd6ad1b676fc0c16c379b3c6f80 (diff)
sched: optimize effective_load()
s_i = S * rw_i / \Sum_j rw_j -> \Sum_j rw_j = S * rw_i / s_i -> s'_i = S * (rw_i + w) / (\Sum_j rw_j + w) delta s = s' - s = S * (rw + w) / ((S * rw / s) + w) = s * (S * (rw + w) / (S * rw + s * w) - 1) a = S*(rw+w), b = S*rw + s*w delta s = s * (a-b) / b IOW, trade one divide for two multiplies Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a1694441f8b7..0d197be3e3e9 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1082,16 +1082,16 @@ static unsigned long effective_load(struct task_group *tg, long wl, int cpu)
for_each_sched_entity(se) {
#define D(n) (likely(n) ? (n) : 1)
- long S, Srw, rw, s, sn;
+ long S, rw, s, a, b;
S = se->my_q->tg->shares;
s = se->my_q->shares;
rw = se->my_q->load.weight;
- Srw = S * rw / D(s);
- sn = S * (rw + wl) / D(Srw + wg);
+ a = S*(rw + wl);
+ b = S*rw + s*wg;
- wl = sn - s;
+ wl = s*(a-b)/D(b);
wg = 0;
#undef D
}