linux-kernel - Re: [PATCH] mm: make __paginginit based on CONFIG_MEMORY

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Date:   Tue, 31 Jul 2018 11:23:33 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     osalvador@...hadventures.net
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        kirill.shutemov@...ux.intel.com, iamjoonsoo.kim@....com,
        Mel Gorman <mgorman@...e.de>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, osalvador@...e.de
Subject: Re: [PATCH] mm: make __paginginit based on CONFIG_MEMORY_HOTPLUG

Yes we free meminit when no CONFIG_MEMORY_HOTPLUG
See here:
http://src.illumos.org/source/xref/linux-master/include/asm-generic/vmlinux.lds.h#107

Pavel
On Tue, Jul 31, 2018 at 11:06 AM Pavel Tatashin
<pasha.tatashin@...cle.com> wrote:
>
> On Tue, Jul 31, 2018 at 11:01 AM Oscar Salvador
> <osalvador@...hadventures.net> wrote:
> >
> > On Tue, Jul 31, 2018 at 10:53:52AM -0400, Pavel Tatashin wrote:
> > > Thats correct on arches where no sparsemem setup_usemap() will not be
> > > freed up. It is a tiny function, just a few instructions. Not a big
> > > deal.
> > >
> > > Pavel
> > > On Tue, Jul 31, 2018 at 10:51 AM Oscar Salvador
> > > <osalvador@...hadventures.net> wrote:
> > > >
> > > > On Tue, Jul 31, 2018 at 10:45:45AM -0400, Pavel Tatashin wrote:
> > > > > Here the patch would look like this:
> > > > >
> > > > > From e640b32dbd329bba5a785cc60050d5d7e1ca18ce Mon Sep 17 00:00:00 2001
> > > > > From: Pavel Tatashin <pasha.tatashin@...cle.com>
> > > > > Date: Tue, 31 Jul 2018 10:37:44 -0400
> > > > > Subject: [PATCH] mm: remove __paginginit
> > > > >
> > > > > __paginginit is the same thing as __meminit except for platforms without
> > > > > sparsemem, there it is defined as __init.
> > > > >
> > > > > Remove __paginginit and use __meminit. Use __ref in one single function
> > > > > that merges __meminit and __init sections: setup_usemap().
> > > > >
> > > > > Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> > > >
> > > > Uhm, I am probably missing something, but with this change, the functions will not be freed up
> > > > while freeing init memory, right?
> > > Thats correct on arches where no sparsemem setup_usemap() will not be
> > > freed up. It is a tiny function, just a few instructions. Not a big
> > > deal.
> >
> > I must be missing something.
> >
> > What about:
> >
> > calc_memmap_size
> > free_area_init_node
> > free_area_init_core
> >
> > These functions are marked with __meminit now.
> > If we have CONFIG_PARSEMEM but not CONFIG_MEMORY_HOTPLUG, these functions will
> > be left there.
>
> I hope we free meminit section if no hotplug configured. If not, than
> sure we should have something like what you suggest not only for these
> functions, but for all other meminit functions in kernel.
>
> >
> > I mean, it is not that it is a big amount, but still.
> >
> > Do not we need something like:
> >
> > diff --git a/include/linux/init.h b/include/linux/init.h
> > index 2538d176dd1f..3b3a88ba80ed 100644
> > --- a/include/linux/init.h
> > +++ b/include/linux/init.h
> > @@ -83,8 +83,12 @@
> >  #define __exit          __section(.exit.text) __exitused __cold notrace
> >
> >  /* Used for MEMORY_HOTPLUG */
> > +#ifdef CONFIG_MEMORY_HOTPLUG
> >  #define __meminit        __section(.meminit.text) __cold notrace \
> >                                                   __latent_entropy
> > +#else
> > +#define __meminit       __init
> > +#endif
> >  #define __meminitdata    __section(.meminit.data)
> >  #define __meminitconst   __section(.meminit.rodata)
> >  #define __memexit        __section(.memexit.text) __exitused __cold notrace
> >
> > on top?
> >
> > Thanks
> > --
> > Oscar Salvador
> > SUSE L3
> >