From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1033864AbdEXIkK (ORCPT ); Wed, 24 May 2017 04:40:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:37430 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1761351AbdEXIkE (ORCPT ); Wed, 24 May 2017 04:40:04 -0400 Date: Wed, 24 May 2017 10:39:57 +0200 From: Michal Hocko To: Heiko Carstens Cc: Gerald Schaefer , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [-next] memory hotplug regression Message-ID: <20170524083956.GC14733@dhcp22.suse.cz> References: <20170524082022.GC5427@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170524082022.GC5427@osiris> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 24-05-17 10:20:22, Heiko Carstens wrote: > Hello Michal, > > I just re-tested linux-next with respect to your memory hotplug changes and > actually (finally) figured out that your patch ("mm, memory_hotplug: do not > associate hotadded memory to zones until online)" changes behaviour on > s390: > > before your patch memory blocks that were offline and located behind the > last online memory block were added by default to ZONE_MOVABLE: > > # cat /sys/devices/system/memory/memory16/valid_zones > Movable Normal > > With your patch this changes, so that they will be added to ZONE_NORMAL by > default instead: > > # cat /sys/devices/system/memory/memory16/valid_zones > Normal Movable > > Sorry, that I didn't realize this earlier! > > Having the ZONE_MOVABLE default was actually the only point why s390's > arch_add_memory() was rather complex compared to other architectures. > > We always had this behaviour, since we always wanted to be able to offline > memory after it was brought online. Given that back then "online_movable" > did not exist, the initial s390 memory hotplug support simply added all > additional memory to ZONE_MOVABLE. > > Keeping the default the same would be quite important. Hmm, that is really unfortunate because I would _really_ like to get rid of the previous semantic which was really awkward. The whole point of the rework is to get rid of the nasty zone shifting. Is it an option to use `online_movable' rather than `online' in your setup? Btw. my long term plan is to remove the zone range constrains altogether so you could online each memblock to the type you want. Would that be sufficient for you in general? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 0ED886B02B4 for ; Wed, 24 May 2017 04:40:00 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id g143so36538149wme.13 for ; Wed, 24 May 2017 01:40:00 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id z9si22083770edb.89.2017.05.24.01.39.58 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 24 May 2017 01:39:58 -0700 (PDT) Date: Wed, 24 May 2017 10:39:57 +0200 From: Michal Hocko Subject: Re: [-next] memory hotplug regression Message-ID: <20170524083956.GC14733@dhcp22.suse.cz> References: <20170524082022.GC5427@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170524082022.GC5427@osiris> Sender: owner-linux-mm@kvack.org List-ID: To: Heiko Carstens Cc: Gerald Schaefer , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed 24-05-17 10:20:22, Heiko Carstens wrote: > Hello Michal, > > I just re-tested linux-next with respect to your memory hotplug changes and > actually (finally) figured out that your patch ("mm, memory_hotplug: do not > associate hotadded memory to zones until online)" changes behaviour on > s390: > > before your patch memory blocks that were offline and located behind the > last online memory block were added by default to ZONE_MOVABLE: > > # cat /sys/devices/system/memory/memory16/valid_zones > Movable Normal > > With your patch this changes, so that they will be added to ZONE_NORMAL by > default instead: > > # cat /sys/devices/system/memory/memory16/valid_zones > Normal Movable > > Sorry, that I didn't realize this earlier! > > Having the ZONE_MOVABLE default was actually the only point why s390's > arch_add_memory() was rather complex compared to other architectures. > > We always had this behaviour, since we always wanted to be able to offline > memory after it was brought online. Given that back then "online_movable" > did not exist, the initial s390 memory hotplug support simply added all > additional memory to ZONE_MOVABLE. > > Keeping the default the same would be quite important. Hmm, that is really unfortunate because I would _really_ like to get rid of the previous semantic which was really awkward. The whole point of the rework is to get rid of the nasty zone shifting. Is it an option to use `online_movable' rather than `online' in your setup? Btw. my long term plan is to remove the zone range constrains altogether so you could online each memblock to the type you want. Would that be sufficient for you in general? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org