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Subject: Re: [PATCH] ARM:mm: define arch-specific IOREMAP_MAX_ORDER only in
 !SMP && !LPAE case
To: Nicolas Pitre <nicolas.pitre@linaro.org>
References: <1441680050-50490-1-git-send-email-zhenzhang.zhang@huawei.com>
 <55EE4BD2.3080800@huawei.com> <55EF24FE.4060602@gmail.com>
 <alpine.LFD.2.20.1509082309040.22877@knanqh.ubzr>
Cc: Zhang Zhen <zhenzhang.zhang@huawei.com>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>, ssantosh@kernel.org,
        vitalya@ti.com, treding@nvidia.com,
        linux-arm-kernel@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Guan Xuetao <gxt@mprc.pku.edu.cn>,
        James Bottomley <JBottomley@parallels.com>,
        Will Deacon <will.deacon@arm.com>,
        Arnd Bergmann <arnd.bergmann@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Safonov <d.safonov@partner.samsung.com>,
        Vladimir Murzin <murzin.v@gmail.com>
From: Sergey Dyasly <dserrg@gmail.com>
Message-ID: <55F07A3E.5010400@gmail.com>
Date: Wed, 9 Sep 2015 21:28:14 +0300
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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@huawei.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