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

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Message-ID: <20121114173928.GK3290@n2100.arm.linux.org.uk>
Date:	Wed, 14 Nov 2012 17:39:28 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 0/3] introduce static_vm for ARM-specific static
	mapped area

On Thu, Nov 15, 2012 at 01:55:51AM +0900, 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.

In what cases?

> We unnecessarily iterate vmlist for finding matched area even if there
> is no static mapped area. And if there are some static mapped areas,
> iterating whole vmlist is not preferable.

Why not?  Please put some explanation into your message rather than
just statements making unexplained assertions.

> Another reason for doing this work is for removing architecture dependency
> on vmalloc layer. I think that vmlist and vmlist_lock is internal data
> structure for vmalloc layer. Some codes for debugging and stat inevitably
> use vmlist and vmlist_lock. But it is preferable that they are used outside
> of vmalloc.c as least as possible.

The vmalloc layer is also made available for ioremap use, and it is
intended that architectures hook into this for ioremap support.
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