On 05/08/2013 07:34 PM, Peter Zijlstra wrote: >> > If we wanted to be more exacting about it we could just give them a >> > sched_slice() worth; this would have a few obvious "nice" properties >> > (pun intended). > Oh I see I misunderstood again :/ Its not about the effective load but weight > of the initial effective load wrt adjustment. > > Previous schedulers didn't have this aspect at all, so no experience from me > here. Paul would be the one, since he's ran longest with this stuff. > > That said, I would tend to keep it shorter rather than longer so that it would > adjust quicker to whatever it really wanted to be. > > Morten says the load is unstable specifically on loaded systems. I would think > this is because we'd experience scheduling latency, we're runnable more > pushing > things up. But if we're really an idle task at heart we'd not run again for a > long while, pushing things down again. > > So on that point Paul's suggestion of maybe starting with __sched_slice() > might > make sense because it increases the weight of the initial avg with nr_running. > > Not sure really, we'll have to play and see what works best for a number of > workloads.
The patch of using sched_slice for review, I am testing the benchmarks --- >From da40ffa90ec1de520bd7e92f5653734a964e3bb2 Mon Sep 17 00:00:00 2001 From: Alex Shi <alex....@intel.com> Date: Thu, 9 May 2013 15:28:34 +0800 Subject: [PATCH 4/8] sched: set initial runnable avg for new task --- kernel/sched/core.c | 2 ++ kernel/sched/fair.c | 15 +++++++++++++++ kernel/sched/sched.h | 2 ++ 3 files changed, 19 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ecec7f1..c17925b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1716,6 +1716,8 @@ void wake_up_new_task(struct task_struct *p) set_task_cpu(p, select_task_rq(p, SD_BALANCE_FORK, 0)); #endif + /* Give new task a start runnable time */ + set_task_runnable_avg(p); rq = __task_rq_lock(p); activate_task(rq, p, 0); p->on_rq = 1; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2881d42..4ec5f29 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -661,6 +661,21 @@ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) return calc_delta_fair(sched_slice(cfs_rq, se), se); } +#ifdef CONFIG_SMP +void set_task_runnable_avg(struct task_struct *p) +{ + u64 slice; + + slice = sched_slice(task_cfs_rq(p), &p->se); + p->se.avg.runnable_avg_sum = slice; + p->se.avg.runnable_avg_period = slice; +} +#else +void set_task_runnable_avg(struct task_struct *p) +{ +} +#endif + /* * Update the current task's runtime statistics. Skip current tasks that * are not in our scheduling class. diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c6634f1..518f3d8a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -900,6 +900,8 @@ extern void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime extern void update_idle_cpu_load(struct rq *this_rq); +extern void set_task_runnable_avg(struct task_struct *p); + #ifdef CONFIG_CGROUP_CPUACCT #include <linux/cgroup.h> /* track cpu usage of a group of tasks and its child groups */ -- 1.7.12 -- Thanks Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/