linux-kernel - Re: [PATCH] ARM:mm: define arch-specific IOREMAP_MAX

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Date:	Wed, 9 Sep 2015 21:28:14 +0300
From:	Sergey Dyasly <dserrg@...il.com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Zhang Zhen <zhenzhang.zhang@...wei.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	ssantosh@...nel.org, vitalya@...com, treding@...dia.com,
	linux-arm-kernel@...ts.infradead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Guan Xuetao <gxt@...c.pku.edu.cn>,
	James Bottomley <JBottomley@...allels.com>,
	Will Deacon <will.deacon@....com>,
	Arnd Bergmann <arnd.bergmann@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Safonov <d.safonov@...tner.samsung.com>,
	Vladimir Murzin <murzin.v@...il.com>
Subject: Re: [PATCH] ARM:mm: define arch-specific IOREMAP_MAX_ORDER only in
 !SMP && !LPAE case

On 09.09.2015 6:10, Nicolas Pitre wrote:
> On Tue, 8 Sep 2015, 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 <zhenzhang.zhang@...wei.com>
>>> ---
>>>    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?
> IMHO the patch makes sense.
>
> Did you send it to RMK's patch system?
Ok, submitted it to the patch system. Thanks!

>
>
> Nicolas

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