linux-kernel - Re: + bootmem-node-setup-agnostic-free

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Date:	Tue, 15 Apr 2008 21:55:03 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	"Yinghai Lu" <yhlu.kernel@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>, akpm@...ux-foundation.org,
	mm-commits@...r.kernel.org, ak@...e.de, clameter@....com,
	kamezawa.hiroyu@...fujitsu.com, y-goto@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: Re: + bootmem-node-setup-agnostic-free_bootmem.patch added to -mm tree

Hi,

"Yinghai Lu" <yhlu.kernel@...il.com> writes:

> On Tue, Apr 15, 2008 at 5:51 AM, Johannes Weiner <hannes@...urebad.de> wrote:
>> Hi Ingo,
>>
>>
>>
>>  Ingo Molnar <mingo@...e.hu> writes:
>>
>>  > * akpm@...ux-foundation.org <akpm@...ux-foundation.org> wrote:
>>  >
>>  >> Subject: bootmem: node-setup agnostic free_bootmem()
>>  >> From: Johannes Weiner <hannes@...urebad.de>
>>  >>
>>  >> Make free_bootmem() look up the node holding the specified address
>>  >> range which lets it work transparently on single-node and multi-node
>>  >> configurations.
>>  >
>>  > this patch does not fix the bug Yinghai's (now dropped) patches solved:
>>  > reserve_early() allocations. So NAK until the full problem has been
>>  > sorted out ...
>>
>>  Okay, NAK on -mm and -x86 for sure.  The patch was meant for mainline
>>  where there is no need for free_bootmem() going across nodes, right?
>>
>>  But I still object to the way Yinghai implemented it.
>>  free_bootmem_core() should not be twisted like this.
>>
>>  How about the following (untested, even uncompiled, but you should get
>>  the idea) proposal which would replace the patch discussed in this
>>  thread:
>>
>>  --- tree-linus.orig/mm/bootmem.c
>>  +++ tree-linus/mm/bootmem.c
>>  @@ -421,7 +421,25 @@ int __init reserve_bootmem(unsigned long
>>
>>
>>   void __init free_bootmem(unsigned long addr, unsigned long size)
>>   {
>>  -       free_bootmem_core(NODE_DATA(0)->bdata, addr, size);
>>  +       bootmem_data_t *bdata;
>>  +
>>  +       list_for_each_entry(bdata, &bdata_list, list) {
>>  +               unsigned long remainder = 0;
>>
>> +
>>  +               if (addr < bdata->node_boot_start)
>>  +                       continue;
>>  +
>>  +               if (PFN_DOWN(addr + size) > bdata->node_low_pfn)
>>  +                       remainder = PFN_DOWN(addr + size) - bdata->node_low_pfn;
>>  +
>>  +               size -= PFN_PHYS(remainder);
>>
>> +               free_bootmem_core(bdata, addr, size)
>>  +
>>  +               if (!remainder)
>>  +                       break;
>>  +
>>  +               addr = PFN_PHYS(bdata->node_low_pfn + 1);
>>  +       }
>>
>>  }
>>
>>   unsigned long __init free_all_bootmem(void)
>
> how about
> 1. bdata is not sorted?

They are kept in a sorted list.  How could they be unsorted?

> 2. intel cross node box: node0: 0g-2g, 4g-6g, node1: 2g-4g, 6g-8g. i
> don't think they have two bdata struct for every node.

How do the bdata structures represent this setup right now?  Are you
sure that there is not a node descriptor for every contiguous region?

	Hannes
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