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

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Date:	Tue, 8 Sep 2015 23:10:30 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Sergey Dyasly <dserrg@...il.com>
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 <murzinv@...il.com>
Subject: Re: [PATCH] ARM:mm: define arch-specific IOREMAP_MAX_ORDER only in
 !SMP && !LPAE case

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?


Nicolas
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