linux-kernel - Re: [PATCH] x86: reuse the boot-time mappings of fixed

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Message-ID: <20090831082632.GB15619@elte.hu>
Date:	Mon, 31 Aug 2009 10:26:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Xiao Guangrong <ericxiao.gr@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jens Axboe <jens.axboe@...cle.com>,
	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	x86@...nel.org, Jeremy Fitzhardinge <jeremy@...p.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: reuse the boot-time mappings of fixed_addresses


* H. Peter Anvin <hpa@...or.com> wrote:

> Ingo Molnar wrote:
>> * Xiao Guangrong <ericxiao.gr@...il.com> wrote:
>>
>>> From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
>>>
>>> Some fixed_addresses items are only used when system boot, after  
>>> boot, they are free but no way to use, like early ioremap area. They 
>>> are wasted for us, we can reuse them after system boot.
>>>
>>> In this patch, we put them in permanent kmap's area and expand  
>>> vmalloc's address range. In boot time, reserve them in  
>>> permanent_kmaps_init() to avoid multiple used, after system boot, we 
>>> unreserved them then user can use it.
>>>
>>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
>>> ---
>>>  arch/x86/include/asm/fixmap.h           |    2 ++
>>>  arch/x86/include/asm/pgtable_32_types.h |    4 ++--
>>>  arch/x86/mm/init_32.c                   |    8 ++++++++
>>>  include/linux/highmem.h                 |    2 ++
>>>  mm/highmem.c                            |   26 ++++++++++++++++++++++++++
>>>  5 files changed, 40 insertions(+), 2 deletions(-)
>>
>> I'm wondering, how much space do we save this way, on a typical bootup 
>> on a typical PC?
>>
>
> Not a huge lot... a few dozen pages.

I guess it's still worth doing - what do you think?

	Ingo
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