linux-kernel - Re: [PATCH v2 08/23] mm/memblock: Add memblock memory allocation apis

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Message-ID: <52A1E4C2.6020004@ti.com>
Date:	Fri, 6 Dec 2013 16:52:50 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
CC:	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 08/23] mm/memblock: Add memblock memory allocation
 apis

On 12/05/2013 10:34 PM, Santosh Shilimkar wrote:
> Grygorii,
>
> On Thursday 05 December 2013 01:48 PM, Strashko, Grygorii wrote:
>> Hi Tejun,
>>
>>> On Thu, Dec 05, 2013 at 06:35:00PM +0200, Grygorii Strashko wrote:
>>>>>> +#define memblock_virt_alloc_align(x, align) \
>>>>>> +  memblock_virt_alloc_try_nid(x, align, BOOTMEM_LOW_LIMIT, \
>>>>>> +                               BOOTMEM_ALLOC_ACCESSIBLE, MAX_NUMNODES)
>>>>>
>>>>> Also, do we really need this align variant separate when the caller
>>>>> can simply specify 0 for the default?
>>>>
>>>> Unfortunately Yes.
>>>> We need it to keep compatibility with bootmem/nobootmem
>>>> which don't handle 0 as default align value.
>>>
>>> Hmm... why wouldn't just interpreting 0 to SMP_CACHE_BYTES in the
>>> memblock_virt*() function work?
>>>
>>
>> Problem is not with memblock_virt*(). The issue will happen in case if
>> memblock or nobootmem are disabled in below code (memblock_virt*() is disabled).
>>
>> +/* Fall back to all the existing bootmem APIs */
>> +#define memblock_virt_alloc(x) \
>> +       __alloc_bootmem(x, SMP_CACHE_BYTES, BOOTMEM_LOW_LIMIT)
>>
>> which will be transformed to
>> +/* Fall back to all the existing bootmem APIs */
>> +#define memblock_virt_alloc(x, align) \
>> +       __alloc_bootmem(x, align, BOOTMEM_LOW_LIMIT)
>>
>> and used as
>>
>> memblock_virt_alloc(size, 0);
>>
>> so, by default bootmem code will use 0 as default alignment and not SMP_CACHE_BYTES
>> and that is wrong.
>>
> Looks like you didn't understood the suggestion completely.
> The fall back inline will look like below .....
>
> static inline memblock_virt_alloc(x, align)
> {
> 	if (align == 0)
> 		align = SMP_CACHE_BYTES
> 	__alloc_bootmem(x, align, BOOTMEM_LOW_LIMIT);
> }
>

I understand. thanks.

Regards,
-grygorii
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