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

[H. Peter Anvin]

Ingo Molnar wrote:
> * Xiao Guangrong <ericxiao.gr@xxxxxxxxx> wrote:
>
> > From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxx>
> > ---
> >  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
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