linux-kernel - [PATCH v1 1/2] mm: drop vm_total

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Date:   Fri, 19 Jun 2020 15:24:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Huang Ying <ying.huang@...el.com>,
        Minchan Kim <minchan@...nel.org>,
        Wei Yang <richard.weiyang@...il.com>
Subject: [PATCH v1 1/2] mm: drop vm_total_pages

The global variable "vm_total_pages" is a relict from older days. There
is only a single user that reads the variable - build_all_zonelists() -
and the first thing it does is updating it. Use a local variable in
build_all_zonelists() instead and drop the local variable.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Wei Yang <richard.weiyang@...il.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/swap.h | 1 -
 mm/memory_hotplug.c  | 3 ---
 mm/page-writeback.c  | 6 ++----
 mm/page_alloc.c      | 2 ++
 mm/vmscan.c          | 5 -----
 5 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 4c5974bb9ba94..124261acd5d0a 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -371,7 +371,6 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
 extern unsigned long shrink_all_memory(unsigned long nr_pages);
 extern int vm_swappiness;
 extern int remove_mapping(struct address_space *mapping, struct page *page);
-extern unsigned long vm_total_pages;
 
 extern unsigned long reclaim_pages(struct list_head *page_list);
 #ifdef CONFIG_NUMA
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9b34e03e730a4..d682781cce48d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -835,8 +835,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	kswapd_run(nid);
 	kcompactd_run(nid);
 
-	vm_total_pages = nr_free_pagecache_pages();
-
 	writeback_set_ratelimit();
 
 	memory_notify(MEM_ONLINE, &arg);
@@ -1586,7 +1584,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
 		kcompactd_stop(node);
 	}
 
-	vm_total_pages = nr_free_pagecache_pages();
 	writeback_set_ratelimit();
 
 	memory_notify(MEM_OFFLINE, &arg);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 28b3e7a675657..4e4ddd67b71e5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2076,13 +2076,11 @@ static int page_writeback_cpu_online(unsigned int cpu)
  * Called early on to tune the page writeback dirty limits.
  *
  * We used to scale dirty pages according to how total memory
- * related to pages that could be allocated for buffers (by
- * comparing nr_free_buffer_pages() to vm_total_pages.
+ * related to pages that could be allocated for buffers.
  *
  * However, that was when we used "dirty_ratio" to scale with
  * all memory, and we don't do that any more. "dirty_ratio"
- * is now applied to total non-HIGHPAGE memory (by subtracting
- * totalhigh_pages from vm_total_pages), and as such we can't
+ * is now applied to total non-HIGHPAGE memory, and as such we can't
  * get into the old insane situation any more where we had
  * large amounts of dirty pages compared to a small amount of
  * non-HIGHMEM memory.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0c435b2ed665c..7b0dde69748c1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5903,6 +5903,8 @@ build_all_zonelists_init(void)
  */
 void __ref build_all_zonelists(pg_data_t *pgdat)
 {
+	unsigned long vm_total_pages;
+
 	if (system_state == SYSTEM_BOOTING) {
 		build_all_zonelists_init();
 	} else {
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b6d84326bdf2d..0010859747df2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -170,11 +170,6 @@ struct scan_control {
  * From 0 .. 200.  Higher means more swappy.
  */
 int vm_swappiness = 60;
-/*
- * The total number of pages which are beyond the high watermark within all
- * zones.
- */
-unsigned long vm_total_pages;
 
 static void set_task_reclaim_state(struct task_struct *task,
 				   struct reclaim_state *rs)
-- 
2.26.2