Subject: [PATCH] ARM:mm: define arch-specific IOREMAP_MAX_ORDER only in !SMP && !LPAE case

From: [email-masked] (Zhang Zhen)
Date: Wed, 9 Sep 2015 09:22:46 +0800

On 2015/9/9 2:12, Sergey Dyasly wrote:
> On 08.09.2015 5:45, Zhang Zhen wrote:
>> The arch-specific IOREMAP_MAX_ORDER is introduced in
>> commit: ff0daca([ARM] Add section support to ioremap) and
>> commit: a069c89 ([ARM] 3705/1: add supersection support to ioremap()).
>> But supersections and sections mappings are only used in !SMP && !LPAE case.
>> Otherwise, mapping is created using the usual 4K pages.
>>
>> In most cases without !SMP && !LPAE, the big alignment cause high fragmentation
>> issue in vmalloc area.
>> Here we use arch-specific IOREMAP_MAX_ORDER only in !SMP && !LPAE case,
>> otherwise use generic IOREMAP_MAX_ORDER in include/linux/vmalloc.h.
>>
>> Signed-off-by: Zhang Zhen <[email-masked]>
>> ---
>>   arch/arm/include/asm/memory.h | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>> index b7f6fb4..3209012 100644
>> --- a/arch/arm/include/asm/memory.h
>> +++ b/arch/arm/include/asm/memory.h
>> @@ -76,10 +76,12 @@
>>    */
>>   #define XIP_VIRT_ADDR(physaddr)  (MODULES_VADDR + ((physaddr) & 0x000fffff))
>>
>> +#if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
>>   /*
>>    * Allow 16MB-aligned ioremap pages
>>    */
>>   #define IOREMAP_MAX_ORDER    24
>> +#endif
>>
>>   #else /* CONFIG_MMU */
>>
> 
> Hmm... This looks exactly like my old patch -
> http://thread.gmane.org/gmane.linux.kernel.mm/127620
> (Thanks to Vladimir for pointing that out!)
> 
> Hasn't there been any progress about this issue?
> 
Oh sorry i didn't notice your old patch.
I send this patch because we encountered high fragmentation issue in vmalloc area
and the link about this issue.
http://lists.infradead.org/pipermail/linux-arm-kernel/2015-January/313040.html
Let's drop my patch.

Besides, i just want to know why this patch is not included into the upstream kernel?

Thanks!
> .