From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: heiko.carstens@de.ibm.com, Tejun Heo <tj@kernel.org>,
Ingo Molnar <mingo@kernel.org>, Rik van Riel <riel@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] sched: select_task_rq() should check cpu_active() like select_fallback_rq()
Date: Mon, 12 Oct 2015 14:16:57 +0200 [thread overview]
Message-ID: <20151012121657.GP3816@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20151010185309.GA24089@redhat.com>
On Sat, Oct 10, 2015 at 08:53:09PM +0200, Oleg Nesterov wrote:
> I do not understand the cpu_active() check in select_fallback_rq().
> x86 doesn't need it, and the recent commit dd9d3843755d "sched: Fix
> cpu_active_mask/cpu_online_mask race" documents the fact that on any
> architecture we can ignore !active starting from CPU_ONLINE stage.
>
> But any possible reason why do we need this check in "fallback" must
> equally apply to select_task_rq().
So the reason, from vague memory, is that we want to allow per-cpu
threads to start/stop before/after active.
active 'should' really only govern load-balancer bits or so.
next prev parent reply other threads:[~2015-10-12 12:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-10 18:52 [PATCH 0/3] (Was: sched: start stopper early) Oleg Nesterov
2015-10-10 18:53 ` [PATCH 1/3] sched: select_task_rq() should check cpu_active() like select_fallback_rq() Oleg Nesterov
2015-10-11 18:04 ` Oleg Nesterov
2015-10-11 18:57 ` Thomas Gleixner
2015-10-12 12:16 ` Peter Zijlstra [this message]
2015-10-12 17:34 ` Oleg Nesterov
2015-10-14 15:00 ` Peter Zijlstra
2015-10-14 20:05 ` Oleg Nesterov
2015-10-14 20:35 ` Peter Zijlstra
2015-10-10 18:53 ` [PATCH 2/3] sched: change select_fallback_rq() to use for_each_cpu_and() Oleg Nesterov
2015-10-10 18:53 ` [PATCH 3/3] sched: don't scan all-offline ->cpus_allowed twice if !CONFIG_CPUSETS Oleg Nesterov
2015-10-20 9:35 ` [tip:sched/core] sched: Don't scan all-offline -> cpus_allowed " tip-bot for Oleg Nesterov
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