linux-kernel - Re: [PATCH v5 0/3] introduce static_vm for ARM-specific static mapped area

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Message-ID: <20130206020942.GD4325@lge.com>
Date:	Wed, 6 Feb 2013 11:09:42 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	Russell King <linux@....linux.org.uk>,
	Nicolas Pitre <nico@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 0/3] introduce static_vm for ARM-specific static
 mapped area

Hello, Santosh.

On Tue, Feb 05, 2013 at 02:32:06PM +0530, Santosh Shilimkar wrote:
> On Tuesday 05 February 2013 06:01 AM, Joonsoo Kim wrote:
> >In current implementation, we used ARM-specific flag, that is,
> >VM_ARM_STATIC_MAPPING, for distinguishing ARM specific static mapped area.
> >The purpose of static mapped area is to re-use static mapped area when
> >entire physical address range of the ioremap request can be covered
> >by this area.
> >
> >This implementation causes needless overhead for some cases.
> >For example, assume that there is only one static mapped area and
> >vmlist has 300 areas. Every time we call ioremap, we check 300 areas for
> >deciding whether it is matched or not. Moreover, even if there is
> >no static mapped area and vmlist has 300 areas, every time we call
> >ioremap, we check 300 areas in now.
> >
> >If we construct a extra list for static mapped area, we can eliminate
> >above mentioned overhead.
> >With a extra list, if there is one static mapped area,
> >we just check only one area and proceed next operation quickly.
> >
> >In fact, it is not a critical problem, because ioremap is not frequently
> >used. But reducing overhead is better idea.
> >
> >Another reason for doing this work is for removing vm_struct list management,
> >entirely. For more information, look at the following link.
> >http://lkml.org/lkml/2012/12/6/184
> >
> 
> [..]
> 
> >
> >Joonsoo Kim (3):
> >   ARM: vmregion: remove vmregion code entirely
> >   ARM: ioremap: introduce an infrastructure for static mapped area
> >   ARM: mm: use static_vm for managing static mapped areas
> >
> >  arch/arm/mm/Makefile   |    2 +-
> >  arch/arm/mm/ioremap.c  |  135 +++++++++++++++++++++----------
> >  arch/arm/mm/mm.h       |   12 +++
> >  arch/arm/mm/mmu.c      |   34 ++++----
> >  arch/arm/mm/vmregion.c |  205 ------------------------------------------------
> >  arch/arm/mm/vmregion.h |   31 --------
> >  6 files changed, 123 insertions(+), 296 deletions(-)
> >  delete mode 100644 arch/arm/mm/vmregion.c
> >  delete mode 100644 arch/arm/mm/vmregion.h
> >
> Nice Clean-up. I tested this series on OMAP which uses few static
> mappings. Feel free to add,
> 
> Tested-by: Santosh Shilimkar<santosh.shilimkar@...com>

I will re-send v6 with your Tested-by.

Thanks for testing this.

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