From: Valentin Schneider <valentin.schneider@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>,
Scott Wood <swood@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mel Gorman <mgorman@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v2 1/3] sched/fair: Call newidle_balance() from balance_callback on PREEMPT_RT
Date: Fri, 07 May 2021 16:19:07 +0100 [thread overview]
Message-ID: <87v97uinbo.mognet@arm.com> (raw)
In-Reply-To: <CAKfTPtBrGF72Zf37vPS6r4wy_jKagznBbiqKWpPyMEB_u4wo1g@mail.gmail.com>
On 05/05/21 14:13, Vincent Guittot wrote:
> On Thu, 29 Apr 2021 at 01:28, Scott Wood <swood@redhat.com> wrote:
>>
>> This is required in order to be able to enable interrupts in the next
>> patch. This is limited to PREEMPT_RT to avoid adding potentially
>> measurable overhead to the non-RT case (requiring a double switch when
>> pulling a task onto a newly idle cpu).
>
> IIUC, only the newidle_balance is a problem and not the idle load
> balance that runs softirq. In this case, why not skipping
> newidle_balance entirely in case of preempt_rt and kick an idle load
> balance instead as you switch to idle thread context anyway
>
So if I follow you, that would be along the lines of having PREEMPT_RT turn
newidle_balance() into:
rq->idle_balance = CPU_IDLE;
rq->next_balance = jiffies;
trigger_load_balance(rq);
which I'm thinking isn't too crazy.
next prev parent reply other threads:[~2021-05-07 15:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 23:28 [PATCH v2 0/3] newidle_balance() PREEMPT_RT latency mitigations Scott Wood
2021-04-28 23:28 ` [PATCH v2 1/3] sched/fair: Call newidle_balance() from balance_callback on PREEMPT_RT Scott Wood
2021-05-05 12:13 ` Vincent Guittot
2021-05-07 15:19 ` Valentin Schneider [this message]
2021-04-28 23:28 ` [PATCH v2 2/3] sched/fair: Enable interrupts when dropping lock in newidle_balance() Scott Wood
2021-04-28 23:28 ` [PATCH v2 3/3] sched/fair: break out of newidle balancing if an RT task appears Scott Wood
2021-04-29 4:11 ` kernel test robot
2021-04-29 6:37 ` kernel test robot
2021-05-07 11:03 ` Peter Zijlstra
2021-05-15 7:29 ` Mike Galbraith
2021-05-15 8:36 ` Mike Galbraith
2021-04-29 7:12 ` [PATCH v2 0/3] newidle_balance() PREEMPT_RT latency mitigations Vincent Guittot
2021-05-01 22:03 ` Scott Wood
2021-05-02 3:25 ` Mike Galbraith
2021-05-03 16:33 ` Scott Wood
2021-05-03 18:52 ` Mike Galbraith
2021-05-03 21:57 ` Scott Wood
2021-05-04 4:07 ` Mike Galbraith
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