Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=647e7cac2d215fb8890f79252d7eaee3d6743d66
Commit: 647e7cac2d215fb8890f79252d7eaee3d6743d66
Parent: 3a2520157234d58abce89526756a32c272824f3f
Author: Ingo Molnar <[EMAIL PROTECTED]>
AuthorDate: Mon Oct 15 17:00:13 2007 +0200
Committer: Ingo Molnar <[EMAIL PROTECTED]>
CommitDate: Mon Oct 15 17:00:13 2007 +0200
sched: vslice fixups for non-0 nice levels
Make vslice accurate wrt nice levels, and add some comments
while we're at it.
Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
Reviewed-by: Thomas Gleixner <[EMAIL PROTECTED]>
---
kernel/sched_fair.c | 53 ++++++++++++++++++++++++++++++++++++++------------
1 files changed, 40 insertions(+), 13 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 32fd976..1f14b56 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -217,6 +217,15 @@ static inline struct sched_entity
*__pick_last_entity(struct cfs_rq *cfs_rq)
* Scheduling class statistics methods:
*/
+
+/*
+ * The idea is to set a period in which each task runs once.
+ *
+ * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
+ * this period because otherwise the slices get too small.
+ *
+ * p = (nr <= nl) ? l : l*nr/nl
+ */
static u64 __sched_period(unsigned long nr_running)
{
u64 period = sysctl_sched_latency;
@@ -230,27 +239,45 @@ static u64 __sched_period(unsigned long nr_running)
return period;
}
+/*
+ * We calculate the wall-time slice from the period by taking a part
+ * proportional to the weight.
+ *
+ * s = p*w/rw
+ */
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- u64 period = __sched_period(cfs_rq->nr_running);
+ u64 slice = __sched_period(cfs_rq->nr_running);
- period *= se->load.weight;
- do_div(period, cfs_rq->load.weight);
+ slice *= se->load.weight;
+ do_div(slice, cfs_rq->load.weight);
- return period;
+ return slice;
}
-static u64 __sched_vslice(unsigned long nr_running)
+/*
+ * We calculate the vruntime slice.
+ *
+ * vs = s/w = p/rw
+ */
+static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)
{
- unsigned long period = sysctl_sched_latency;
- unsigned long nr_latency = sysctl_sched_nr_latency;
+ u64 vslice = __sched_period(nr_running);
- if (unlikely(nr_running > nr_latency))
- nr_running = nr_latency;
+ do_div(vslice, rq_weight);
- period /= nr_running;
+ return vslice;
+}
- return (u64)period;
+static u64 sched_vslice(struct cfs_rq *cfs_rq)
+{
+ return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running);
+}
+
+static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ return __sched_vslice(cfs_rq->load.weight + se->load.weight,
+ cfs_rq->nr_running + 1);
}
/*
@@ -469,10 +496,10 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity
*se, int initial)
vruntime >>= 1;
}
} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)
- vruntime += __sched_vslice(cfs_rq->nr_running)/2;
+ vruntime += sched_vslice(cfs_rq)/2;
if (initial && sched_feat(START_DEBIT))
- vruntime += __sched_vslice(cfs_rq->nr_running + 1);
+ vruntime += sched_vslice_add(cfs_rq, se);
if (!initial) {
if (sched_feat(NEW_FAIR_SLEEPERS))
-
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