Messages in this thread Patch in this message | | | Date | Fri, 24 Oct 2008 11:06:16 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 5/8] sched: virtual time buddy preemption |
| |
Since we moved wakeup preemption back to virtual time, it makes sense to move the buddy stuff back as well. The purpose of the buddy scheduling is to allow a quickly scheduling pair of tasks to run away from the group as far as a regular busy task would be allowed under wakeup preemption.
This has the advantage that the pair can ping-pong for a while, enjoying cache-hotness. Without buddy scheduling other tasks would interleave destroying the cache.
Also, it saves a word in cfs_rq.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- kernel/sched.c | 1 - kernel/sched_fair.c | 12 +++++------- 2 files changed, 5 insertions(+), 8 deletions(-)
Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -385,7 +385,6 @@ struct cfs_rq { u64 exec_clock; u64 min_vruntime; - u64 pair_start; struct rb_root tasks_timeline; struct rb_node *rb_leftmost; Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -790,16 +790,14 @@ set_next_entity(struct cfs_rq *cfs_rq, s se->prev_sum_exec_runtime = se->sum_exec_runtime; } +static int +wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); + static struct sched_entity * pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se) { - struct rq *rq = rq_of(cfs_rq); - u64 pair_slice = rq->clock - cfs_rq->pair_start; - - if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) { - cfs_rq->pair_start = rq->clock; + if (!cfs_rq->next || wakeup_preempt_entity(cfs_rq->next, se) == 1) return se; - } return cfs_rq->next; } --
| |