From 3d6357de8aa09e1966770dc1171c72679946464f Mon Sep 17 00:00:00 2001 From: Arun KS Date: Fri, 28 Dec 2018 00:34:20 -0800 Subject: mm: reference totalram_pages and managed_pages once per function Patch series "mm: convert totalram_pages, totalhigh_pages and managed pages to atomic", v5. This series converts totalram_pages, totalhigh_pages and zone->managed_pages to atomic variables. totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better to remove the lock and convert variables to atomic. With the change, preventing poteintial store-to-read tearing comes as a bonus. This patch (of 4): This is in preparation to a later patch which converts totalram_pages and zone->managed_pages to atomic variables. Please note that re-reading the value might lead to a different value and as such it could lead to unexpected behavior. There are no known bugs as a result of the current code but it is better to prevent from them in principle. Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org Signed-off-by: Arun KS Reviewed-by: Konstantin Khlebnikov Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Acked-by: Vlastimil Babka Reviewed-by: Pavel Tatashin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- net/dccp/proto.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'net/dccp') diff --git a/net/dccp/proto.c b/net/dccp/proto.c index 2cc5fbb1b29e..ff727ff61b5b 100644 --- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -1131,6 +1131,7 @@ EXPORT_SYMBOL_GPL(dccp_debug); static int __init dccp_init(void) { unsigned long goal; + unsigned long nr_pages = totalram_pages; int ehash_order, bhash_order, i; int rc; @@ -1157,10 +1158,10 @@ static int __init dccp_init(void) * * The methodology is similar to that of the buffer cache. */ - if (totalram_pages >= (128 * 1024)) - goal = totalram_pages >> (21 - PAGE_SHIFT); + if (nr_pages >= (128 * 1024)) + goal = nr_pages >> (21 - PAGE_SHIFT); else - goal = totalram_pages >> (23 - PAGE_SHIFT); + goal = nr_pages >> (23 - PAGE_SHIFT); if (thash_entries) goal = (thash_entries * -- cgit v1.2.3-59-g8ed1b