From: Peter Zijlstra <peterz@infradead.org>
To: "Ofer Levi(SW)" <oferle@mellanox.com>
Cc: "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
"vatsa@in.ibm.com" <vatsa@in.ibm.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"Vineet.Gupta1@synopsys.com" <Vineet.Gupta1@synopsys.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: hotplug support for arch/arc/plat-eznps platform
Date: Mon, 7 Aug 2017 17:10:20 +0200 [thread overview]
Message-ID: <20170807151020.h2u45tx64ccee64a@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <VI1PR0501MB211071DC936129CBC5C4A397B2B50@VI1PR0501MB2110.eurprd05.prod.outlook.com>
On Mon, Aug 07, 2017 at 01:41:38PM +0000, Ofer Levi(SW) wrote:
> > You've failed to explain why you think hotplug should be a performance
> > critical path.
> 1. hotplug bring up of 4K cpus takes 40 minutes. Way too much for any user.
> 2. plat-eznps is a network processor, where bring up time is sensitive.
But who is doing actual hotplug? Why would you ever unplug or plug a CPU
in a time critical situation?
> > I'm also not seeing how it would be different from boot; you'd be
> > looking at a similar cost for SMP bringup.
> bring up time of 4k cpus during kernel boot takes 4.5 minutes.
> The function in question is performed only when smp init was performed.
> If I understand correctly, whatever this function is doing is performed after all cpus
> were brought up during kernel boot.
Doesn't make sense. If you look at smp_init() boot brings up the CPUs
one at a time.
So how can boot be different than hot-pugging them?
next prev parent reply other threads:[~2017-08-07 15:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-06 5:53 hotplug support for arch/arc/plat-eznps platform Ofer Levi(SW)
2017-08-07 8:33 ` Peter Zijlstra
2017-08-07 13:41 ` Ofer Levi(SW)
2017-08-07 15:10 ` Peter Zijlstra [this message]
2017-08-08 6:49 ` Ofer Levi(SW)
2017-08-08 10:16 ` Peter Zijlstra
2017-08-09 15:19 ` Ofer Levi(SW)
2017-08-09 15:34 ` Peter Zijlstra
2017-08-10 7:40 ` Ofer Levi(SW)
2017-08-10 9:19 ` Peter Zijlstra
2017-08-10 11:51 ` Ofer Levi(SW)
2017-08-10 15:45 ` Peter Zijlstra
2017-08-14 7:54 ` Ofer Levi(SW)
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