linux-kernel - Re: [PATCH -v3 14/14] x86, mm: Map ISA area with connected ram range at the same time

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Date:	Thu, 6 Sep 2012 10:22:19 +0300 (EEST)
From:	Pekka Enberg <penberg@...nel.org>
To:	Yinghai Lu <yinghai@...nel.org>
cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -v3 14/14] x86, mm: Map ISA area with connected ram range
 at the same time

On Wed, Sep 5, 2012 at 1:02 AM, Pekka Enberg <penberg@...nel.org> wrote:
> > How significant is the speed gain? The "isa_done" flag makes code flow
> > more difficult to follow.

On Wed, 5 Sep 2012, Yinghai Lu wrote:
> Not really much.
> 
> when booting system:
> memmap=16m$128m memmap=16m$512m memmap=16m$256m memmap=16m$768m memmap=16m$1024m
> 
> with the patch
> [    0.000000] init_memory_mapping: [mem 0x00000000-0x07ffffff]
> [    0.000000]  [mem 0x00000000-0x07ffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x09000000-0x0fffffff]
> [    0.000000]  [mem 0x09000000-0x0fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x11000000-0x1fffffff]
> [    0.000000]  [mem 0x11000000-0x1fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x21000000-0x2fffffff]
> [    0.000000]  [mem 0x21000000-0x2fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x31000000-0x3fffffff]
> [    0.000000]  [mem 0x31000000-0x3fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x41000000-0x7fffdfff]
> [    0.000000]  [mem 0x41000000-0x7fdfffff] page 2M
> [    0.000000]  [mem 0x7fe00000-0x7fffdfff] page 4k
> 
> otherwise will have
> 
> [    0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff]
> [    0.000000]  [mem 0x00000000-0x000fffff] page 4k
> [    0.000000] init_memory_mapping: [mem 0x00100000-0x07ffffff]
> [    0.000000]  [mem 0x00100000-0x001fffff] page 4k
> [    0.000000]  [mem 0x00200000-0x07ffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x09000000-0x0fffffff]
> [    0.000000]  [mem 0x09000000-0x0fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x11000000-0x1fffffff]
> [    0.000000]  [mem 0x11000000-0x1fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x21000000-0x2fffffff]
> [    0.000000]  [mem 0x21000000-0x2fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x31000000-0x3fffffff]
> [    0.000000]  [mem 0x31000000-0x3fffffff] page 2M
> [    0.000000] init_memory_mapping: [mem 0x41000000-0x7fffdfff]
> [    0.000000]  [mem 0x41000000-0x7fdfffff] page 2M
> [    0.000000]  [mem 0x7fe00000-0x7fffdfff] page 4k

OK. Is there any other reason than performance to do this?

			Pekka
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