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

H. Peter Anvin
2009-08-29T18:18:07Z

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.

-hpa