Messages in this thread | | | Date | Mon, 24 Jun 2013 13:04:24 +0200 | Subject | Re: [Resend patch v8 06/13] sched: compute runnable load avg in cpu_load and cpu_avg_load_per_task | From | Vincent Guittot <> |
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On 24 June 2013 11:06, Alex Shi <alex.shi@intel.com> wrote: > On 06/20/2013 10:18 AM, Alex Shi wrote: >> They are the base values in load balance, update them with rq runnable >> load average, then the load balance will consider runnable load avg >> naturally. >> >> We also try to include the blocked_load_avg as cpu load in balancing, >> but that cause kbuild performance drop 6% on every Intel machine, and >> aim7/oltp drop on some of 4 CPU sockets machines. >> Or only add blocked_load_avg into get_rq_runable_load, hackbench still >> drop a little on NHM EX. >> >> Signed-off-by: Alex Shi <alex.shi@intel.com> >> Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com> > > > I am sorry for still having some swing on cfs and rt task load consideration. > So give extra RFC patch to consider RT load in balance. > With or without this patch, my test result has no change, since there is no > much RT tasks in my testing. > > I am not familiar with RT scheduler, just rely on PeterZ who is experts on this. :) > > --- > > From b9ed5363b0a579a87256b589278c8c66500c7db3 Mon Sep 17 00:00:00 2001 > From: Alex Shi <alex.shi@intel.com> > Date: Mon, 24 Jun 2013 16:12:29 +0800 > Subject: [PATCH 08/16] sched: recover to whole rq load include rt tasks' > > patch 'sched: compute runnable load avg in cpu_load and > cpu_avg_load_per_task' weight rq's load on cfs.runnable_load_avg instead > of rq->load.weight. That is fine when system has no much RT load. > > But if there are lots of RT load on rq, that code will just > weight the cfs tasks in load balance without consideration of RT, that
AFAICT, the RT tasks activity is already taken into account by decreasing the cpu_power that is used during load balance like in the find_busiest_queue where weighted_cpuload is divided by cpu_power.
Vincent
> may cause load imbalance if much RT load isn't imbalanced among cpu. > Using rq->avg.load_avg_contrib can resolve this problem and keep the > advantages from runnable load balance. > > BTW, this patch may increase the balance failed times, if move_tasks can > not balance loads between CPUs, like there is only RT load in CPUs. > > Signed-off-by: Alex Shi <alex.shi@intel.com> > --- > kernel/sched/fair.c | 4 ++-- > kernel/sched/proc.c | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 37a5720..6979906 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2968,7 +2968,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) > /* Used instead of source_load when we know the type == 0 */ > static unsigned long weighted_cpuload(const int cpu) > { > - return cpu_rq(cpu)->cfs.runnable_load_avg; > + return cpu_rq(cpu)->avg.load_avg_contrib; > } > > /* > @@ -3013,7 +3013,7 @@ static unsigned long cpu_avg_load_per_task(int cpu) > { > struct rq *rq = cpu_rq(cpu); > unsigned long nr_running = ACCESS_ONCE(rq->nr_running); > - unsigned long load_avg = rq->cfs.runnable_load_avg; > + unsigned long load_avg = rq->avg.load_avg_contrib; > > if (nr_running) > return load_avg / nr_running; > diff --git a/kernel/sched/proc.c b/kernel/sched/proc.c > index ce5cd48..4f2490c 100644 > --- a/kernel/sched/proc.c > +++ b/kernel/sched/proc.c > @@ -504,7 +504,7 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load, > #ifdef CONFIG_SMP > unsigned long get_rq_runnable_load(struct rq *rq) > { > - return rq->cfs.runnable_load_avg; > + return rq->avg.load_avg_contrib; > } > #else > unsigned long get_rq_runnable_load(struct rq *rq) > -- > 1.7.12 > >
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