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From: Dou Liyang <douly.fnst@cn.fujitsu.com>
To: Thomas Gleixner <tglx@linutronix.de>, Ming Lei <ming.lei@redhat.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>,
	Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	<linux-kernel@vger.kernel.org>, <linux-block@vger.kernel.org>,
	Laurence Oberman <loberman@redhat.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH V3 0/4] genirq/affinity: irq vector spread among online CPUs as far as possible
Date: Tue, 13 Mar 2018 11:11:02 +0800	[thread overview]
Message-ID: <5e5f3852-5314-c479-245e-d0a575e533a5@cn.fujitsu.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1803091531000.1364@nanos.tec.linutronix.de>

Hi Thomas,

At 03/09/2018 11:08 PM, Thomas Gleixner wrote:
[...]
> 
> I'm not sure if there is a clear indicator whether physcial hotplug is
> supported or not, but the ACPI folks (x86) and architecture maintainers
+cc Rafael

> should be able to answer that question. I have a machine which says:
> 
>     smpboot: Allowing 128 CPUs, 96 hotplug CPUs
> 
> There is definitely no way to hotplug anything on that machine and sure the

AFAIK, in ACPI based dynamic reconfiguration, there is no clear
indicator. In theory, If the ACPI tables have the hotpluggable
CPU resources, the OS can support physical hotplug.

For your machine, Did your CPUs support multi-threading, but not enable
it?

And, sometimes we should not trust the number of possible CPUs. I also
met the situation that BIOS told to ACPI that it could support physical
CPUs hotplug, But actually, there was no hardware slots in the machine.
the ACPI tables like user inputs which should be validated when we use.

> existing spread algorithm will waste vectors to no end.
> 
> Sure then there is virt, which can pretend to have a gazillion of possible
> hotpluggable CPUs, but virt is an insanity on its own. Though someone might
> come up with reasonable heuristics for that as well.
> 
> Thoughts?

Do we have to map the vectors to CPU statically? Can we map them when
we hotplug/enable the possible CPU?

Thanks,

	dou

  reply	other threads:[~2018-03-13  3:11 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-08 10:53 [PATCH V3 0/4] genirq/affinity: irq vector spread among online CPUs as far as possible Ming Lei
2018-03-08 10:53 ` [PATCH V3 1/4] genirq/affinity: rename *node_to_possible_cpumask as *node_to_cpumask Ming Lei
2018-04-06 21:52   ` [tip:irq/core] genirq/affinity: Rename " tip-bot for Ming Lei
2018-03-08 10:53 ` [PATCH V3 2/4] genirq/affinity: move actual irq vector spread into one helper Ming Lei
2018-04-06 21:53   ` [tip:irq/core] genirq/affinity: Move actual irq vector spreading into a helper function tip-bot for Ming Lei
2018-03-08 10:53 ` [PATCH V3 3/4] genirq/affinity: support to do irq vectors spread starting from any vector Ming Lei
2018-04-06 21:53   ` [tip:irq/core] genirq/affinity: Allow irq spreading from a given starting point tip-bot for Ming Lei
2018-03-08 10:53 ` [PATCH V3 4/4] genirq/affinity: irq vector spread among online CPUs as far as possible Ming Lei
2018-04-03 13:32   ` Thomas Gleixner
2018-04-03 16:00     ` Ming Lei
2018-04-04  8:25       ` Thomas Gleixner
2018-04-04 12:45         ` Thomas Gleixner
2018-04-04 15:20           ` Ming Lei
2018-04-05 10:12             ` Thomas Gleixner
2018-04-04 15:08         ` Ming Lei
2018-04-04 19:38           ` Thomas Gleixner
2018-04-06  9:13             ` Ming Lei
2018-04-06  9:46               ` Thomas Gleixner
2018-04-06 21:49                 ` Thomas Gleixner
2018-04-08  3:19                   ` Ming Lei
2018-04-06 21:54   ` [tip:irq/core] genirq/affinity: Spread irq vectors among present " tip-bot for Ming Lei
2018-03-08 13:18 ` [PATCH V3 0/4] genirq/affinity: irq vector spread among online " Artem Bityutskiy
2018-03-08 13:25   ` Artem Bityutskiy
2018-03-08 13:34   ` Ming Lei
2018-03-08 23:20     ` Thomas Gleixner
2018-03-09  1:24       ` Ming Lei
2018-03-09  7:00         ` Artem Bityutskiy
2018-03-09  7:33           ` Ming Lei
2018-03-09 10:08         ` Thomas Gleixner
2018-03-09 12:08           ` Ming Lei
2018-03-09 15:08             ` Thomas Gleixner
2018-03-13  3:11               ` Dou Liyang [this message]
2018-03-13  7:38                 ` Artem Bityutskiy
2018-03-13  7:38                   ` Artem Bityutskiy
2018-03-13  8:35                   ` Ming Lei
2018-03-13  8:39                     ` Artem Bityutskiy
2018-03-13  8:39                       ` Artem Bityutskiy
2018-03-13  9:35                       ` Rafael J. Wysocki
2018-03-14  3:29                         ` Dou Liyang
2018-03-14  4:11                           ` Dou Liyang
2018-03-14  9:07                             ` Artem Bityutskiy
2018-03-14  9:47                               ` Dou Liyang
2018-03-13  9:25                 ` Rafael J. Wysocki
2018-03-14  3:30                   ` Dou Liyang
2018-03-30  3:15               ` Ming Lei
2018-04-03 12:55                 ` Thomas Gleixner
2018-03-26  8:39   ` Thorsten Leemhuis
2018-03-28  6:15     ` Artem Bityutskiy

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