From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id 20C166B2360 for ; Tue, 20 Nov 2018 21:52:34 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id w2so1835663edc.13 for ; Tue, 20 Nov 2018 18:52:34 -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 s4sor7919279edx.12.2018.11.20.18.52.32 for (Google Transport Security); Tue, 20 Nov 2018 18:52:32 -0800 (PST) Date: Wed, 21 Nov 2018 02:52:31 +0000 From: Wei Yang Subject: Re: [PATCH] mm, hotplug: protect nr_zones with pgdat_resize_lock() Message-ID: <20181121025231.ggk7zgq53nmqsqds@master> Reply-To: Wei Yang References: <20181120014822.27968-1-richard.weiyang@gmail.com> <20181120073141.GY22247@dhcp22.suse.cz> <3ba8d8c524d86af52e4c1fddc2d45734@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ba8d8c524d86af52e4c1fddc2d45734@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: osalvador@suse.de Cc: Michal Hocko , Wei Yang , akpm@linux-foundation.org, linux-mm@kvack.org On Tue, Nov 20, 2018 at 08:58:11AM +0100, osalvador@suse.de wrote: >> On the other hand I would like to see the global lock to go away because >> it causes scalability issues and I would like to change it to a range >> lock. This would make this race possible. >> >> That being said this is more of a preparatory work than a fix. One could >> argue that pgdat resize lock is abused here but I am not convinced a >> dedicated lock is much better. We do take this lock already and spanning >> its scope seems reasonable. An update to the documentation is due. > >Would not make more sense to move it within the pgdat lock >in move_pfn_range_to_zone? >The call from free_area_init_core is safe as we are single-thread there. > Agree. This would be better. >And if we want to move towards a range locking, I even think it would be more >consistent if we move it within the zone's span lock (which is already >wrapped with a pgdat lock). > I lost a little here, just want to confirm with you. Instead of call pgdat_resize_lock() around init_currently_empty_zone() in move_pfn_range_to_zone(), we move init_currently_empty_zone() before resize_zone_range()? This sounds reasonable. > > -- Wei Yang Help you, Help me