From 6189eb82f0aec8a877190bf52e629c687ed02773 Mon Sep 17 00:00:00 2001 From: Pasha Tatashin Date: Fri, 13 Jan 2023 15:42:53 +0000 Subject: mm/page_ext: do not allocate space for page_ext->flags if not needed There is 8 byte page_ext->flags field allocated per page whenever CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext uses flags. Therefore, check whether flags is needed at least by one user and if so allocate space for it. For example when page_table_check is enabled, on a machine with 128G of memory before the fix: [ 2.244288] allocated 536870912 bytes of page_ext after the fix: [ 2.160154] allocated 268435456 bytes of page_ext Also, add a kernel-doc comment before page_ext_operations that describes the fields, and remove check if need() is set, as that is now a required field. [pasha.tatashin@soleen.com: address comments from Mike Rapoport] Link: https://lkml.kernel.org/r/20230117202103.1412449-1-pasha.tatashin@soleen.com Link: https://lkml.kernel.org/r/20230113154253.92480-1-pasha.tatashin@soleen.com Signed-off-by: Pasha Tatashin Acked-by: David Hildenbrand Acked-by: Vlastimil Babka Acked-by: David Rientjes Reviewed-by: Mike Rapoport (IBM) Cc: Charan Teja Kalla Cc: Li Zhe Cc: Michal Hocko Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/page_table_check.c | 1 + 1 file changed, 1 insertion(+) (limited to 'mm/page_table_check.c') diff --git a/mm/page_table_check.c b/mm/page_table_check.c index 93e633c1d587..25d8610c0042 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -45,6 +45,7 @@ struct page_ext_operations page_table_check_ops = { .size = sizeof(struct page_table_check), .need = need_page_table_check, .init = init_page_table_check, + .need_shared_flags = false, }; static struct page_table_check *get_page_table_check(struct page_ext *page_ext) -- cgit v1.2.3-58-ga151