From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Yinghai Lu <yinghai@kernel.org>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"ananth@in.ibm.com" <ananth@in.ibm.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus.
Date: Wed, 13 Jan 2010 14:00:29 -0800 [thread overview]
Message-ID: <4B4E427D.9090207@zytor.com> (raw)
In-Reply-To: <87tyupfzk8.fsf@basil.nowhere.org>
On 01/13/2010 01:46 PM, Andi Kleen wrote:
> Yinghai Lu <yinghai@kernel.org> writes:
>>
>> so you want to treat those disabled cpus in the those system as hotplug cpus or not?
>
> Why not? It's not that a hotplug cpu is particularly expensive.
> It's just a bunch of memory and not even very much of it.
>
> White and blacklists just to save a small amount of memory
> seem like a bad idea.
>
There are configurations in which percpu memory is in the megabytes.
This is exactly why we need high water mark allocation of percpu memory:
for configurations where there are possible hotpluggable CPU sockets
(which may be virtual, and a lot larger number than necessary) we
shouldn't need to allocate memory for a processor which has never been
added and is net unlikely to ever be added. The only alternative is to
go to great length to keep the
(percpu memory) x (possible cpus - actual cpus) product as small as
possible, which is shortchanging the utility of the percpu memory system.
-hpa
next prev parent reply other threads:[~2010-01-13 22:02 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-12 23:17 [PATCH 0/5] clean up logical flat apic mode using Yinghai Lu
2010-01-12 23:17 ` [PATCH -v2 1/5] use nr_cpus= to set nr_cpu_ids early Yinghai Lu
2010-01-12 23:17 ` [PATCH 2/5] x86: using logical flat for amd cpu too Yinghai Lu
2010-01-12 23:17 ` [PATCH -v2 3/5] x86: according to nr_cpu_ids to decide if need to leave logical flat Yinghai Lu
2010-01-12 23:17 ` [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus Yinghai Lu
2010-01-12 23:56 ` Suresh Siddha
2010-01-13 0:05 ` Yinghai Lu
2010-01-13 1:48 ` Suresh Siddha
2010-01-13 1:55 ` Yinghai Lu
2010-01-13 2:06 ` Suresh Siddha
2010-01-13 2:13 ` Yinghai Lu
2010-01-13 2:21 ` Suresh Siddha
2010-01-13 2:26 ` Yinghai Lu
2010-01-13 21:46 ` Andi Kleen
2010-01-13 22:00 ` H. Peter Anvin [this message]
2010-01-13 22:23 ` Andi Kleen
2010-01-13 22:27 ` H. Peter Anvin
2010-01-13 22:29 ` Suresh Siddha
2010-01-13 22:36 ` H. Peter Anvin
2010-01-13 22:49 ` Suresh Siddha
2010-01-13 23:02 ` Yinghai Lu
2010-01-13 23:13 ` H. Peter Anvin
2010-01-13 23:52 ` Andi Kleen
2010-01-14 9:25 ` Andi Kleen
2010-01-12 23:17 ` [PATCH 4/5] x86: make 32bit apic flat to physflat switch like 64bit Yinghai Lu
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