From fa004ab7365ffa1e17e6b267d64798afccb94946 Mon Sep 17 00:00:00 2001 From: Wei Yang Date: Fri, 28 Dec 2018 00:37:10 -0800 Subject: mm, hotplug: move init_currently_empty_zone() under zone_span_lock protection During online_pages phase, pgdat->nr_zones will be updated in case this zone is empty. Currently the online_pages phase is protected by the global locks (device_device_hotplug_lock and mem_hotplug_lock), which ensures there is no contention during the update of nr_zones. These global locks introduces scalability issues (especially the second one), which slow down code relying on get_online_mems(). This is also a preparation for not having to rely on get_online_mems() but instead some more fine grained locks. The patch moves init_currently_empty_zone under both zone_span_writelock and pgdat_resize_lock because both the pgdat state is changed (nr_zones) and the zone's start_pfn. Also this patch changes the documentation of node_size_lock to include the protection of nr_zones. Link: http://lkml.kernel.org/r/20181203205016.14123-1-richard.weiyang@gmail.com Signed-off-by: Wei Yang Acked-by: Michal Hocko Reviewed-by: Oscar Salvador Cc: David Hildenbrand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index fc4b5cdb6c2d..cc4a507d7ca4 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -636,8 +636,8 @@ typedef struct pglist_data { #endif #if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT) /* - * Must be held any time you expect node_start_pfn, node_present_pages - * or node_spanned_pages stay constant. + * Must be held any time you expect node_start_pfn, + * node_present_pages, node_spanned_pages or nr_zones to stay constant. * * pgdat_resize_lock() and pgdat_resize_unlock() are provided to * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG -- cgit v1.2.3-59-g8ed1b