Change CFS into a virtual deadline scheduler. By flattening the grouping hierarchy into a single level we now end up with tasks that have varying latency requirements. Tasks from group A might have a larger latency period than those from group B as the period depends on the number of runnable tasks within a group. The current scheduling criteria does not take that into account - it assumes a single latency period. In order to accommodate these varying latencies in the scheduling decision, move to EDF [*] scheduling. We treat the tasks need + its latency period as the deadline it has to meet. This includes the latency into the scheduling decision. [*] - EDF is correct up until load 1, after that it is not a closed system so improvement is possible here. It is usable because the system strives to generate the load 1 situation. Signed-off-by: Peter Zijlstra --- include/linux/sched.h | 1 + kernel/sched_fair.c | 6 +++++- 2 files changed, 6 insertions(+), 1 deletion(-) Index: linux-2.6/include/linux/sched.h =================================================================== --- linux-2.6.orig/include/linux/sched.h +++ linux-2.6/include/linux/sched.h @@ -925,6 +925,7 @@ struct sched_entity { u64 exec_start; u64 sum_exec_runtime; u64 vruntime; + u64 vperiod; u64 prev_sum_exec_runtime; #ifdef CONFIG_SCHEDSTATS Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -220,9 +220,11 @@ static inline u64 min_vruntime(u64 min_v static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) { - return se->vruntime - cfs_rq->min_vruntime; + return se->vruntime + se->vperiod - cfs_rq->min_vruntime; } +static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se); + /* * Enqueue an entity into the rb-tree: */ @@ -240,6 +242,8 @@ static void __enqueue_entity(struct cfs_ if (se == cfs_rq->curr) return; + se->vperiod = sched_vslice_add(cfs_rq, se); + cfs_rq = &rq_of(cfs_rq)->cfs; link = &cfs_rq->tasks_timeline.rb_node; -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/