linux-kernel - Re: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus.

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Message-ID: <4B4D2811.7000001@kernel.org>
Date:	Tue, 12 Jan 2010 17:55:29 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as
 hotplug cpus.

On 01/12/2010 05:48 PM, Suresh Siddha wrote:
> On Tue, 2010-01-12 at 16:05 -0800, Yinghai Lu wrote:
>> On 01/12/2010 03:56 PM, Suresh Siddha wrote:
>>> On Tue, 2010-01-12 at 15:17 -0800, Yinghai Lu wrote:
>>>> some systems that have disable cpus entries because same
>>>>   BIOS will support 2 sockets and 4 sockets and more at
>>>>   same time, BIOS just leave some disable entries, but
>>>>   those system do not support cpu hotplug. we don't need
>>>>   treat disabled_cpus as hotplug cpus.
>>>> so we can make nr_cpu_ids smaller and save more space
>>>>   (pcpu data allocations), and could make some systems run
>>>>   with logical flat instead of physical flat apic mode
>>>>
>>>> -v2: change to black list instead
>>>
>>> I don't think this list will work because every HT system with HT
>>> disabled in the bios shows that logical cpu as disabled.
>>
>> so you want to treat those disabled cpus in the those system as hotplug cpus or not?
> 
> They are really not hot plug cpus, so they can also take advantage of
> what you are trying to provide with this patch.

you mean this blacklist could be too long?

switch to whitelist for the box can treat disabled cpus as hotplug cpus?

> 
> Also I am very confused with what exactly you are doing with the dmi
> list..
> 
> +        printk(KERN_NOTICE "%s detected: treat disabled cpus as hotplug ones\n", d->ident);
> +        treat_disabled_cpus_as_hotplug = 0;
> 
sorry, forget to change the print out.

YH
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