Re: [PATCH] x86: reuse the boot-time mappings of fixed_addresses

Ingo Molnar
2009-08-31T08:27:27Z

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

> Ingo Molnar wrote:
>> * Xiao Guangrong <ericxiao.gr@gmail.com> wrote:
>>
>>> From: Xiao Guangrong <xiaoguangrong@cn.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@cn.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