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Date:   Fri, 19 Jun 2020 13:47:14 +0000
From:   Wei Yang <richard.weiyang@gmail.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@suse.com>,
        Huang Ying <ying.huang@intel.com>,
        Minchan Kim <minchan@kernel.org>,
        Wei Yang <richard.weiyang@gmail.com>
Subject: Re: [PATCH v1 1/2] mm: drop vm_total_pages
Message-ID: <20200619134714.yaxol5ckemhffgqm@master>
Reply-To: Wei Yang <richard.weiyang@gmail.com>
References: <20200619132410.23859-1-david@redhat.com>
 <20200619132410.23859-2-david@redhat.com>
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On Fri, Jun 19, 2020 at 03:24:09PM +0200, David Hildenbrand wrote:
>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@linux-foundation.org>
>Cc: Johannes Weiner <hannes@cmpxchg.org>
>Cc: Michal Hocko <mhocko@suse.com>
>Cc: Huang Ying <ying.huang@intel.com>
>Cc: Minchan Kim <minchan@kernel.org>
>Cc: Wei Yang <richard.weiyang@gmail.com>
>Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Wei Yang <richard.weiyang@gmail.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

-- 
Wei Yang
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