From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id E0E596B0279 for ; Wed, 24 May 2017 17:51:06 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id p74so205775110pfd.11 for ; Wed, 24 May 2017 14:51:06 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id e3si7452770plk.67.2017.05.24.14.51.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 May 2017 14:51:06 -0700 (PDT) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v4OLn212125222 for ; Wed, 24 May 2017 17:51:05 -0400 Received: from e34.co.us.ibm.com (e34.co.us.ibm.com [32.97.110.152]) by mx0a-001b2d01.pphosted.com with ESMTP id 2anh76jn65-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 24 May 2017 17:51:05 -0400 Received: from localhost by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 24 May 2017 15:51:04 -0600 Date: Wed, 24 May 2017 16:50:56 -0500 From: Reza Arbab Subject: Re: [RFC PATCH 1/2] mm, memory_hotplug: drop artificial restriction on online/offline References: <20170524122411.25212-1-mhocko@kernel.org> <20170524122411.25212-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20170524122411.25212-2-mhocko@kernel.org> Message-Id: <20170524215056.h4r3sdk23bn4c2sr@arbab-laptop.localdomain> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Jerome Glisse , Yasuaki Ishimatsu , qiuxishi@huawei.com, Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Andi Kleen , David Rientjes , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , LKML , Michal Hocko On Wed, May 24, 2017 at 02:24:10PM +0200, Michal Hocko wrote: >74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL >memory") has added can_offline_normal which checks the amount of >memory in !movable zones as long as CONFIG_MOVABLE_NODE is disable. >It disallows to offline memory if there is nothing left with a >justification that "memory-management acts bad when we have nodes which >is online but don't have any normal memory". > >74d42d8fe146 ("memory_hotplug: ensure every online node has NORMAL >memory") has introduced a restriction that every numa node has to have >at least some memory in !movable zones before a first movable memory >can be onlined if !CONFIG_MOVABLE_NODE with the same justification > >While it is true that not having _any_ memory for kernel allocations on >a NUMA node is far from great and such a node would be quite subotimal >because all kernel allocations will have to fallback to another NUMA >node but there is no reason to disallow such a configuration in >principle. > >Besides that there is not really a big difference to have one memblock >for ZONE_NORMAL available or none. With 128MB size memblocks the system >might trash on the kernel allocations requests anyway. It is really >hard to draw a line on how much normal memory is really sufficient so >we have to rely on administrator to configure system sanely therefore >drop the artificial restriction and remove can_offline_normal and >can_online_high_movable altogether. I'm really liking all this cleanup of the memory hotplug code. Thanks! Much appreciated. Acked-by: Reza Arbab -- Reza Arbab -- 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