linux-kernel - [PATCH] mm, memory_hotplug: update pcp lists everytime onlining a memory block

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Date:   Sun,  2 Aug 2020 18:24:56 +0530
From:   Charan Teja Reddy <charante@...eaurora.org>
To:     akpm@...ux-foundation.org, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, vinmenon@...eaurora.org,
        Charan Teja Reddy <charante@...eaurora.org>
Subject: [PATCH] mm, memory_hotplug: update pcp lists everytime onlining a memory block

When onlining a first memory block in a zone, pcp lists are not updated
thus pcp struct will have the default setting of ->high = 0,->batch = 1.
This means till the second memory block in a zone(if it have) is onlined
the pcp lists of this zone will not contain any pages because pcp's
->count is always greater than ->high thus free_pcppages_bulk() is
called to free batch size(=1) pages every time system wants to add a
page to the pcp list through free_unref_page(). To put this in a word,
system is not using benefits offered by the pcp lists when there is a
single onlineable memory block in a zone. Correct this by always
updating the pcp lists when memory block is onlined.

Signed-off-by: Charan Teja Reddy <charante@...eaurora.org>
---
 mm/memory_hotplug.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index dcdf327..7f62d69 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -854,8 +854,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	node_states_set_node(nid, &arg);
 	if (need_zonelists_rebuild)
 		build_all_zonelists(NULL);
-	else
-		zone_pcp_update(zone);
+	zone_pcp_update(zone);
 
 	init_per_zone_wmark_min();
 
-- 
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