The patch titled
Subject: mm/page_ext.c: make page_ext_init a noop when CONFIG_PAGE_EXTENSION but nothing uses it
has been added to the -mm tree. Its filename is
mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it.patch
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From: Oscar Salvador <osalvador@xxxxxxxxxxxxxxxxxx>
Subject: mm/page_ext.c: make page_ext_init a noop when CONFIG_PAGE_EXTENSION but nothing uses it
static struct page_ext_operations *page_ext_ops[] always contains debug_guardpage_ops,
static struct page_ext_operations *page_ext_ops[] = {
&debug_guardpage_ops,
#ifdef CONFIG_PAGE_OWNER
&page_owner_ops,
#endif
...
}
but for it to work, CONFIG_DEBUG_PAGEALLOC must be enabled first. If
someone has CONFIG_PAGE_EXTENSION, but has none of its users, eg:
(CONFIG_PAGE_OWNER, CONFIG_DEBUG_PAGEALLOC, CONFIG_IDLE_PAGE_TRACKING), we
can shrink page_ext_init() to a simple retq.
$ size vmlinux (before patch)
text data bss dec hex filename
14356698 5681582 1687748 21726028 14b834c vmlinux
$ size vmlinux (after patch)
text data bss dec hex filename
14356008 5681538 1687748 21725294 14b806e vmlinux
On the other hand, it might does not even make sense, since if someone
enables CONFIG_PAGE_EXTENSION, I would expect him to enable also at least
one of its users.
Link: http://lkml.kernel.org/r/20180105130235.GA21241@xxxxxxxxxxxxxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_ext.c | 2 ++
1 file changed, 2 insertions(+)
diff -puN mm/page_ext.c~mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it mm/page_ext.c
--- a/mm/page_ext.c~mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it
+++ a/mm/page_ext.c
@@ -59,7 +59,9 @@
*/
static struct page_ext_operations *page_ext_ops[] = {
+#ifdef CONFIG_DEBUG_PAGEALLOC
&debug_guardpage_ops,
+#endif
#ifdef CONFIG_PAGE_OWNER
&page_owner_ops,
#endif
_
Patches currently in -mm which might be from osalvador@xxxxxxxxxxxxxxxxxx are
mm-page_owner-remove-drain_all_pages-from-init_early_allocated_pages.patch
mm-slab-remove-redundant-assignments-for-slab_state.patch
mm-memory_hotplug-remove-unnecesary-check-from-register_page_bootmem_info_section.patch
mm-memory_hotplug-remove-second-__nr_to_section-in-register_page_bootmem_info_section.patch
mm-page_owner-clean-up-init_pages_in_zone.patch
mm-page_extc-make-page_ext_init-a-noop-when-config_page_extension-but-nothing-uses-it.patch
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