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

Ingo Molnar
2009-08-29T11:02:13Z

* 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?

Ingo