From: Jason Low <jason.low2@hp.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"mingo@kernel.org" <mingo@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
"riel@redhat.com" <riel@redhat.com>,
"vincent.guittot@linaro.org" <vincent.guittot@linaro.org>,
"pjt@google.com" <pjt@google.com>,
"benh@kernel.crashing.org" <benh@kernel.crashing.org>,
"efault@gmx.de" <efault@gmx.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"iamjoonsoo.kim@lge.com" <iamjoonsoo.kim@lge.com>,
"svaidy@linux.vnet.ibm.com" <svaidy@linux.vnet.ibm.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
jason.low2@hp.com
Subject: Re: sched: Improve load balancing in the presence of idle CPUs
Date: Wed, 08 Apr 2015 14:22:49 -0700 [thread overview]
Message-ID: <1428528169.3506.34.camel@j-VirtualBox> (raw)
In-Reply-To: <20150408111216.GA24645@linux.vnet.ibm.com>
On Wed, 2015-04-08 at 16:42 +0530, Srikar Dronamraju wrote:
> * Jason Low <jason.low2@hp.com> [2015-04-07 17:07:46]:
>
> > On Tue, 2015-04-07 at 16:28 -0700, Jason Low wrote:
> >
> > > Okay, so perhaps we can also try continuing nohz load balancing if we
> > > find that there are overloaded CPUs in the system.
> >
> > Something like the following.
> >
> > ---
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index fdae26e..d636bf7 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -7620,6 +7620,16 @@ out:
> > }
> >
> > #ifdef CONFIG_NO_HZ_COMMON
> > +static inline bool nohz_kick_needed(struct rq *rq);
> > +
> > +static inline void pass_nohz_balance(struct rq *this_rq, int this_cpu)
> > +{
> > + clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
> > + nohz.next_balance = jiffies;
>
> Why are we updating nohz.next_balance here?
This was just to make sure that since we're continuing the balancing on
another CPU that the nohz next_balance is guaranteed to be "now".
> > + if (nohz_kick_needed(this_rq))
> > + nohz_balancer_kick();
> > +}
> > +
> > /*
> > * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
> > * rebalancing for all the cpus for whom scheduler ticks are stopped.
> > @@ -7631,8 +7641,10 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
> > int balance_cpu;
> >
> > if (idle != CPU_IDLE ||
>
> Would it make sense to add need_resched here like
> http://mid.gmane.org/1427442750-8112-1-git-send-email-wanpeng.li@linux.intel.com
Yeah, we could have incorporated adding the need_resched there too for
testing purposes.
Though that probably wouldn't make too much of a difference in
performance with this patch, since this also modified the need_resched()
check in the loop + nohz.next_balance. So I think it would still be fine
to test this without the added need_resched().
next prev parent reply other threads:[~2015-04-08 21:23 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-30 18:55 sched: Improve load balancing in the presence of idle CPUs Jason Low
2015-03-31 8:37 ` Preeti U Murthy
2015-03-31 18:54 ` Jason Low
2015-04-01 6:49 ` Preeti U Murthy
2015-04-01 17:04 ` Morten Rasmussen
2015-04-02 3:30 ` Jason Low
2015-04-02 8:49 ` Morten Rasmussen
2015-04-02 5:59 ` Jason Low
2015-04-02 8:42 ` Preeti U Murthy
2015-04-02 9:17 ` Morten Rasmussen
2015-04-02 17:22 ` Jason Low
2015-04-03 22:35 ` Tim Chen
2015-04-07 17:42 ` Jason Low
2015-04-07 19:39 ` Tim Chen
2015-04-07 20:24 ` Jason Low
2015-04-04 9:59 ` Preeti U Murthy
2015-04-07 23:28 ` Jason Low
2015-04-08 0:07 ` Jason Low
2015-04-08 11:12 ` Srikar Dronamraju
2015-04-08 21:22 ` Jason Low [this message]
2015-04-10 8:37 ` Srikar Dronamraju
2015-04-13 18:55 ` Jason Low
2015-04-13 20:54 ` Jason Low
2015-04-09 2:39 ` Jason Low
2015-04-09 7:02 ` Srikar Dronamraju
2015-04-09 22:49 ` Jason Low
2015-04-13 6:16 ` Preeti U Murthy
2015-04-13 22:49 ` Jason Low
2015-04-14 2:59 ` Jason Low
2015-04-02 2:11 ` Jason Low
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