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

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Message-ID: <CAMj1kXFfmXMriLutNA1FyeNhNz=Zo2hHgO8FLkQ3_xT8kF6oeQ@mail.gmail.com>
Date:   Mon, 13 Jun 2022 11:44:19 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     mawupeng <mawupeng1@...wei.com>
Cc:     Jonathan Corbet <corbet@....net>, Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>, aou@...s.berkeley.edu,
        paulmck@...nel.org, keescook@...omium.org,
        songmuchun@...edance.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, swboyd@...omium.org,
        wei.liu@...nel.org, robin.murphy@....com, david@...hat.com,
        Anshuman Khandual <anshuman.khandual@....com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        wangkefeng.wang@...wei.com, gpiccoli@...lia.com,
        chenhuacai@...nel.org, geert@...ux-m68k.org,
        vijayb@...ux.microsoft.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v4 6/6] memblock: Disable mirror feature if kernelcore is
 not specified

On Mon, 13 Jun 2022 at 11:13, mawupeng <mawupeng1@...wei.com> wrote:
>
>
>
> On 6/13/2022 4:21 PM, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@...wei.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@...wei.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@...nel.org>

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