linux-kernel - Re: [PATCH v4 4/6] x86/mm: Introduce CONFIG_KEEP

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Message-ID: <CAPcyv4hXpqrZ4jmgmjy9fH=3oHg0UDDU6xLGX2TVCgSS_xkq4w@mail.gmail.com>
Date:   Thu, 13 Feb 2020 13:19:51 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>
Subject: Re: [PATCH v4 4/6] x86/mm: Introduce CONFIG_KEEP_NUMA

On Thu, Feb 13, 2020 at 1:32 AM Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Dan Williams <dan.j.williams@...el.com> wrote:
>
> > Currently x86 numa_meminfo is marked __initdata in the
> > CONFIG_MEMORY_HOTPLUG=n case. In support of a new facility to allow
> > drivers to map reserved memory to a 'target_node'
> > (phys_to_target_node()), add support for removing the __initdata
> > designation for those users. Both memory hotplug and
> > phys_to_target_node() users select CONFIG_KEEP_NUMA to tell the arch to
> > maintain its physical address to numa mapping infrastructure post init.
> >
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Cc: Andy Lutomirski <luto@...nel.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: "H. Peter Anvin" <hpa@...or.com>
> > Cc: <x86@...nel.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: David Hildenbrand <david@...hat.com>
> > Cc: Michal Hocko <mhocko@...e.com>
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > ---
> >  arch/x86/mm/numa.c   |    6 +-----
> >  include/linux/numa.h |    6 ++++++
> >  mm/Kconfig           |    5 +++++
> >  3 files changed, 12 insertions(+), 5 deletions(-)
>
> The concept and the x86 portions look sane, just a few minor nits:
>
> >
> > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > index 99f7a68738f0..5289d9d6799a 100644
> > --- a/arch/x86/mm/numa.c
> > +++ b/arch/x86/mm/numa.c
> > @@ -25,11 +25,7 @@ nodemask_t numa_nodes_parsed __initdata;
> >  struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
> >  EXPORT_SYMBOL(node_data);
> >
> > -static struct numa_meminfo numa_meminfo
> > -#ifndef CONFIG_MEMORY_HOTPLUG
> > -__initdata
> > -#endif
> > -;
> > +static struct numa_meminfo numa_meminfo __initdata_numa;
> >
> >  static int numa_distance_cnt;
> >  static u8 *numa_distance;
> > diff --git a/include/linux/numa.h b/include/linux/numa.h
> > index 20f4e44b186c..c005ed6b807b 100644
> > --- a/include/linux/numa.h
> > +++ b/include/linux/numa.h
> > @@ -13,6 +13,12 @@
> >
> >  #define      NUMA_NO_NODE    (-1)
> >
> > +#ifdef CONFIG_KEEP_NUMA
> > +#define __initdata_numa
> > +#else
> > +#define __initdata_numa __initdata
> > +#endif
> > +
> >  #ifdef CONFIG_NUMA
> >  int numa_map_to_online_node(int node);
> >  #else
> > diff --git a/mm/Kconfig b/mm/Kconfig
> > index ab80933be65f..001f1185eadf 100644
> > --- a/mm/Kconfig
> > +++ b/mm/Kconfig
> > @@ -139,6 +139,10 @@ config HAVE_FAST_GUP
> >  config ARCH_KEEP_MEMBLOCK
> >       bool
> >
> > +# Keep arch numa mapping infrastructure post-init.
>
> s/numa/NUMA
>
> Please also capitalize consistently in the rest of the series.
>
> > +config KEEP_NUMA
> > +     bool
>
>
> So most of our recent new NUMA options followed the naming pattern of:
>
>   CONFIG_NUMA_*
>
> Such as CONFIG_NUMA_BALANCING or CONFIG_NUMA_EMU.
>
> So I'd suggesting naming it to CONFIG_NUMA_KEEP, or, a bit more
> descriptively, such as CONFIG_NUMA_KEEP_MAPPING or such?
>
> 'Keeping NUMA' is kind of lame - of course we keep NUMA. ;-)

Ok, I settled on CONFIG_NUMA_KEEP_MEMINFO, and will fix up the
lowercase "numa" instances in the set.