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

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Message-ID: <20180731150115.GC1499@techadventures.net>
Date:   Tue, 31 Jul 2018 17:01:15 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
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

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 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