On Sat, 2015-10-10 at 22:03 +0800, kbuild test robot wrote:
> Hi Mike,
Hi there pin-the-tail-on-the-donkey bot. Eeee Ahhh :)
sched: disable task group wide utilization based weight on the desktop
Task group wide utilization based weight may work well for servers, but it
is horrible on the desktop. 8 groups of 1 hog demoloshes interactivity, 1
group of 8 hogs has noticable impact, 2 such groups is very very noticable.
Turn it off if autogroup is enabled, and add a feature to let people set the
definition of fair to what serves them best. For the desktop, fixed group
weight wins hands down, no contest....
Signed-off-by: Mike Galbraith <umgwanakikb...@gmail.com>
---
kernel/sched/fair.c | 5 +++++
kernel/sched/features.h | 14 ++++++++++++++
---
kernel/sched/fair.c | 5 +++++
kernel/sched/features.h | 14 ++++++++++++++
2 files changed, 19 insertions(+)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2372,6 +2372,8 @@ static long calc_cfs_shares(struct cfs_r
{
long tg_weight, load, shares;
+ if (!sched_feat(SMP_FAIR_GROUPS))
+ return tg->shares;
tg_weight = calc_tg_weight(tg, cfs_rq);
load = cfs_rq_load_avg(cfs_rq);
@@ -2423,6 +2425,9 @@ static void update_cfs_shares(struct cfs
#ifndef CONFIG_SMP
if (likely(se->load.weight == tg->shares))
return;
+#else
+ if (!sched_feat(SMP_FAIR_GROUPS) && se->load.weight == tg->shares)
+ return;
#endif
shares = calc_cfs_shares(cfs_rq, tg);
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -88,3 +88,17 @@ SCHED_FEAT(LB_MIN, false)
*/
SCHED_FEAT(NUMA, true)
#endif
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+/*
+ * With SMP_FAIR_GROUPS set, activity group wide determines share for
+ * all froup members. This does very bad things to interactivity when
+ * a desktop box is heavily loaded. Default to off when autogroup is
+ * enabled, and let all users set it to what works best for them.
+ */
+#if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)
+SCHED_FEAT(SMP_FAIR_GROUPS, true)
+#else
+SCHED_FEAT(SMP_FAIR_GROUPS, false)
+#endif
+#endif
--
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