From: Andi Kleen <andi@firstfloor.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Lameter <cl@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
tj@kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org,
linux-arch@vger.kernel.org, andi@firstfloor.org, hpa@zytor.com,
tglx@linutronix.de
Subject: Re: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support
Date: Wed, 1 Jul 2009 08:34:55 +0200 [thread overview]
Message-ID: <20090701063455.GL6760@one.firstfloor.org> (raw)
In-Reply-To: <20090630230743.GA17968@elte.hu>
> Say it says "256 CPUs".
>
> But i only run a 2 CPU guest system. But i want to run it with the
> _on demand capability_ to scale up to 256 virtual CPUs if needed,
> without having to reboot the guest and without having to allocate
> all the percpu space for 256 CPUs beforehand. Ok?
Then you would need to fix lots of subsystems. Everyone doing
for_each_possible_cpu() today and not having a cpu notifier callback.
git/linux-2.6% gid for_each_possible_cpu | wc -l
247
git/linux-2.6% gid CPU_UP_PREPARE | wc -l
48
Essentially you would discard the concept of possible CPUs
and replace it only with online CPUs, but possible CPUs
are widely used.
It's unclear to me it's worth all that work (and how to test
it properly), assuming we fix the few per cpu pigs today that make it
very expensive to preallocate percpu in the big debug configurations.
> It is a simple, basic OS feature and concept.
.. that Linux doesn't support without some heavy lifting.
Not answering emails will not change that fact.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2009-07-01 6:35 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-24 13:30 [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support Tejun Heo
2009-06-24 13:30 ` [PATCH 01/10] x86: make pcpu_chunk_addr_search() matching stricter Tejun Heo
2009-06-24 13:30 ` [PATCH 02/10] percpu: drop @unit_size from embed first chunk allocator Tejun Heo
2009-06-24 13:30 ` [PATCH 03/10] x86,percpu: generalize 4k " Tejun Heo
2009-06-24 13:30 ` [PATCH 04/10] percpu: make 4k first chunk allocator map memory Tejun Heo
2009-07-13 10:12 ` David Howells
2009-07-15 3:17 ` Tejun Heo
2009-06-24 13:30 ` [PATCH 05/10] x86,percpu: generalize lpage first chunk allocator Tejun Heo
2009-06-24 13:30 ` [PATCH 06/10] percpu: simplify pcpu_setup_first_chunk() Tejun Heo
2009-06-24 13:30 ` [PATCH 07/10] percpu: reorder a few functions in mm/percpu.c Tejun Heo
2009-06-24 13:30 ` [PATCH 08/10] percpu: drop pcpu_chunk->page[] Tejun Heo
2009-06-24 13:30 ` [PATCH 09/10] percpu: allow non-linear / sparse cpu -> unit mapping Tejun Heo
2009-06-24 13:30 ` [PATCH 10/10] percpu: teach large page allocator about NUMA Tejun Heo
2009-06-24 23:55 ` [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support Andrew Morton
2009-06-25 0:02 ` Andi Kleen
2009-06-25 0:13 ` H. Peter Anvin
2009-06-25 9:19 ` Andi Kleen
2009-06-25 14:18 ` H. Peter Anvin
2009-06-25 19:54 ` Andi Kleen
2009-06-25 20:15 ` H. Peter Anvin
2009-06-25 20:26 ` Andi Kleen
2009-06-26 0:40 ` Tejun Heo
2009-06-26 2:02 ` H. Peter Anvin
2009-06-26 6:54 ` Andi Kleen
2009-06-25 2:35 ` Tejun Heo
2009-06-25 9:20 ` Ingo Molnar
2009-06-29 23:20 ` Christoph Lameter
2009-06-29 23:39 ` Andrew Morton
2009-06-30 14:24 ` Christoph Lameter
2009-06-30 19:15 ` Ingo Molnar
2009-06-30 19:39 ` Christoph Lameter
2009-06-30 20:21 ` Scott Lurndal
2009-06-30 21:31 ` Ingo Molnar
2009-06-30 22:16 ` Christoph Lameter
2009-06-30 22:31 ` Ingo Molnar
2009-06-30 22:40 ` Andi Kleen
2009-07-01 0:48 ` Tejun Heo
2009-06-30 22:55 ` Christoph Lameter
2009-06-30 23:07 ` Ingo Molnar
2009-06-30 23:18 ` Christoph Lameter
2009-06-30 23:30 ` Ingo Molnar
2009-07-01 6:34 ` Andi Kleen [this message]
2009-06-30 23:20 ` Tejun Heo
2009-06-30 23:31 ` Ingo Molnar
2009-06-30 23:34 ` H. Peter Anvin
2009-07-01 6:42 ` Andi Kleen
2009-07-01 10:21 ` Tejun Heo
2009-07-01 12:23 ` Andi Kleen
2009-07-01 12:53 ` Tejun Heo
2009-07-01 13:11 ` Andi Kleen
2009-07-01 17:33 ` Christoph Lameter
2009-07-01 22:42 ` Tejun Heo
2009-07-03 23:14 ` Tejun Heo
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