From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 8D54D6B6B04 for ; Mon, 3 Dec 2018 15:50:49 -0500 (EST) Received: by mail-pg1-f198.google.com with SMTP id h9so7584515pgm.1 for ; Mon, 03 Dec 2018 12:50:49 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id o19sor19517506pll.44.2018.12.03.12.50.47 for (Google Transport Security); Mon, 03 Dec 2018 12:50:47 -0800 (PST) From: Wei Yang Subject: [PATCH v4] mm, hotplug: move init_currently_empty_zone() under zone_span_lock protection Date: Tue, 4 Dec 2018 04:50:16 +0800 Message-Id: <20181203205016.14123-1-richard.weiyang@gmail.com> In-Reply-To: <20181130065847.13714-1-richard.weiyang@gmail.com> References: <20181130065847.13714-1-richard.weiyang@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@suse.com, osalvador@suse.de, david@redhat.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, Wei Yang 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. Signed-off-by: Wei Yang Acked-by: Michal Hocko Reviewed-by: Oscar Salvador CC: David Hildenbrand --- v4: * mention the preparation for improving scalability by David's comment v3: * slightly modify the last paragraph of changelog based on Michal's comment v2: * commit log changes * modify the code in move_pfn_range_to_zone() instead of in init_currently_empty_zone() * pgdat_resize_lock documentation change --- include/linux/mmzone.h | 7 ++++--- mm/memory_hotplug.c | 5 ++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 3d0c472438d2..37d9c5c3faa6 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -635,9 +635,10 @@ 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. Holding this will also - * guarantee that any pfn_valid() stays that way. + * Must be held any time you expect node_start_pfn, + * node_present_pages, node_spanned_pages or nr_zones stay constant. + * Holding this will also guarantee that any pfn_valid() stays that + * way. * * pgdat_resize_lock() and pgdat_resize_unlock() are provided to * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 61972da38d93..f626e7e5f57b 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -742,14 +742,13 @@ void __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, int nid = pgdat->node_id; unsigned long flags; - if (zone_is_empty(zone)) - init_currently_empty_zone(zone, start_pfn, nr_pages); - clear_zone_contiguous(zone); /* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */ pgdat_resize_lock(pgdat, &flags); zone_span_writelock(zone); + if (zone_is_empty(zone)) + init_currently_empty_zone(zone, start_pfn, nr_pages); resize_zone_range(zone, start_pfn, nr_pages); zone_span_writeunlock(zone); resize_pgdat_range(pgdat, start_pfn, nr_pages); -- 2.15.1