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SubjectRe: 2.6.24-git4+ regression

* Lukas Hejtmanek <xhejtman@ics.muni.cz> wrote:

> I noticed short thread in LKM regarding "sched: add vslice" causes
> horrible interactivity under load.
>
> I can see similar behavior. If I stress both CPU cores, even typing on
> keyboard suffers from huge latencies, I can see letters appearing with
> delay (typing into xterm). No swap is used at all, having 1GB free
> RAM.
>
> I noticed this bad behavior with 2.6.24-git[46], 2.6.24-rc8-git was
> OK.

if you apply the current sched-fixes (rollup patch below), does it get
any better?

Ingo

Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -520,7 +520,7 @@ place_entity(struct cfs_rq *cfs_rq, stru

if (!initial) {
/* sleeps upto a single latency don't count. */
- if (sched_feat(NEW_FAIR_SLEEPERS) && entity_is_task(se))
+ if (sched_feat(NEW_FAIR_SLEEPERS))
vruntime -= sysctl_sched_latency;

/* ensure we never gain time by being placed backwards. */
@@ -1106,7 +1106,11 @@ static void check_preempt_wakeup(struct
}

gran = sysctl_sched_wakeup_granularity;
- if (unlikely(se->load.weight != NICE_0_LOAD))
+ /*
+ * More easily preempt - nice tasks, while not making
+ * it harder for + nice tasks.
+ */
+ if (unlikely(se->load.weight > NICE_0_LOAD))
gran = calc_delta_fair(gran, &se->load);

if (pse->vruntime + gran < se->vruntime)

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