Re: [PATCH v4 6/6] memblock: Disable mirror feature if kernelcore is not specified

[Ard Biesheuvel <ardb@kernel.org>]

On Mon, 13 Jun 2022 at 11:13, mawupeng <mawupeng1@huawei.com> wrote:
>
>
>
> On 6/13/2022 4:21 PM, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@huawei.com>
> >
> > If system have some mirrored memory and mirrored feature is not specified
> > in boot parameter, the basic mirrored feature will be enabled and this will
> > lead to the following situations:
> >
> > - memblock memory allocation prefers mirrored region. This may have some
> >   unexpected influence on numa affinity.
> >
> > - contiguous memory will be split into several parts if parts of them
> >   is mirrored memory via memblock_mark_mirror().
> >
> > To fix this, variable mirrored_kernelcore will be checked in
> > memblock_mark_mirror(). Mark mirrored memory with flag MEMBLOCK_MIRROR iff
> > kernelcore=mirror is added in the kernel parameters.
> >
> > Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> > ---
> >  mm/internal.h   | 2 ++
> >  mm/memblock.c   | 3 +++
> >  mm/page_alloc.c | 2 +-
> >  3 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/internal.h b/mm/internal.h
> > index c0f8fbe0445b..ddd2d6a46f1b 100644
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -861,4 +861,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
> >
> >  DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
> >
> > +extern bool mirrored_kernelcore;
> > +
> >  #endif       /* __MM_INTERNAL_H */
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index b1d2a0009733..a9f18b988b7f 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -924,6 +924,9 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
> >   */
> >  int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
> >  {
> > +     if (!mirrored_kernelcore)
> > +             return 0;
> > +
> >       system_has_some_mirror = true;
> >
> >       return memblock_setclr_flag(base, size, 1, MEMBLOCK_MIRROR);
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index e008a3df0485..9b030aeb4983 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -356,7 +356,7 @@ static unsigned long required_kernelcore_percent __initdata;
> >  static unsigned long required_movablecore __initdata;
> >  static unsigned long required_movablecore_percent __initdata;
> >  static unsigned long zone_movable_pfn[MAX_NUMNODES] __initdata;
> > -static bool mirrored_kernelcore __meminitdata;
> > +bool mirrored_kernelcore __initdata;
>
> __initdata here is not suitable and will lead to compile warnings.
>
> In my test, __initdata_memblock and ro_after_init are both fine, but I am not
> sure which one to choose? Do you have any idea on this?
>

__initdata_memblock is fine if it works.

This looks to me like the right place to implement this policy, so

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> >
> >  /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
> >  int movable_zone;