linux-kernel - Re: [PATCH 16/35] x86: make 64 bit use early

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Date:	Thu, 25 Feb 2010 11:07:53 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Christoph Lameter <cl@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 16/35] x86: make 64 bit use early_res instead of bootmem
 before slab

Hello, Yinghai.

On 02/25/2010 08:32 AM, Yinghai Lu wrote:
>>> Kernel panic - not syncing: free_early on not reserved area: 2f80000-2f9ffff!
>>> Pid: 0, comm: swapper Not tainted 2.6.33-rc8-tip-00918-gb34d361 #159
>>> Call Trace:	
>>>  [<ffffffff815d12e2>] panic+0x84/0x147
>>>  [<ffffffff81cceecb>] free_early+0x64/0x6d
>>>  [<ffffffff81cd2231>] free_bootmem+0xc/0xe
>>>  [<ffffffff81cc1cd6>] pcpu_fc_free+0x1d/0x1f
>>>  [<ffffffff81cd6056>] pcpu_embed_first_chunk+0x13a/0x27f
>>>  [<ffffffff81cc1cd8>] ? pcpu_fc_alloc+0x0/0xac
>>>  [<ffffffff81cc1cb9>] ? pcpu_fc_free+0x0/0x1f
>>>  [<ffffffff81cc1af7>] setup_per_cpu_areas+0x82/0x239
>>>  [<ffffffff81cb5b3c>] start_kernel+0x1b8/0x43b
>>>  [<ffffffff81cb52bc>] x86_64_start_reservations+0xa7/0xab
>>>  [<ffffffff81cb53b8>] x86_64_start_kernel+0xf8/0x107
>>>
>>
>> we can not handle partial free, and current only user for that is pcpu_setup...
> 
> any plan to pcpu_setup to use slab allocation instead of bootmem?
> that code is only one user that do partial bootmem free.

The problem is that the pcpu_embed_first_chunk() allocator depends on
having a large contiguous slab of memory to overlay the percpu
variables and then giving back the unused parts (due to layout and
cpu_possible_mask not being contiguous).  There's no way to do partial
alloc/free anymore?

Thanks.

-- 
tejun
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