From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9DFCC43219 for ; Thu, 25 Apr 2019 15:42:10 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1DC90206C1 for ; Thu, 25 Apr 2019 15:42:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BsyEDrOS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DC90206C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=hgPGkk9QLPkvufMSc6wjc7xSsGPhi+5uqpjZJFjVq+w=; b=BsyEDrOSpF0GDs R+1z4/aYn4F40PFYFpHwbeeFP+C7Wzfx/l3fModAiYyqYALZ0MRRwMwnH++H970FddQxKDnRfWsZU c3gMqYJOw/bYcZ2o2lMHi3+46pik0bCBxh496KGGj/BRwJZP3oozeyRfMDjKzq39VpfS7OeBT8g9b fLjRqN9qa0t+mZfqefmGQVp/Jvb2EB43SNpTS4wE6+X3yrW2CtSBnftB2jY3NW6AeF1mRqzcBJZl+ x51QHG2RQj6wzuUvJvWPTr7Ub6o2VnVJWNBW5xjiC/Z4JzRC7q2VASdNV/XbW8BG6Xm7bIWbPOkci R6aX9Bt8Qw0Dx5l4IPhg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJgVf-0001wW-1X; Thu, 25 Apr 2019 15:42:03 +0000 Received: from mx2.suse.de ([195.135.220.15] helo=mx1.suse.de) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJgVb-0001vo-Ow for linux-arm-kernel@lists.infradead.org; Thu, 25 Apr 2019 15:42:01 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C7F89AFED; Thu, 25 Apr 2019 15:41:57 +0000 (UTC) Date: Thu, 25 Apr 2019 17:41:56 +0200 From: Michal Hocko To: Will Deacon Subject: Re: [PATCH] arm64: configurable sparsemem section size Message-ID: <20190425154156.GZ12751@dhcp22.suse.cz> References: <20190423203843.2898-1-pasha.tatashin@soleen.com> <20190425152550.GY12751@dhcp22.suse.cz> <20190425153138.GC25193@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190425153138.GC25193@fuggles.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190425_084159_990129_974C16CC X-CRM114-Status: GOOD ( 19.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tiwai@suse.de, catalin.marinas@arm.com, dave.hansen@linux.intel.com, keith.busch@intel.com, linux-mm@kvack.org, baiyaowei@cmss.chinamobile.com, zwisler@kernel.org, sashal@kernel.org, dave.jiang@intel.com, linux-nvdimm@lists.01.org, vishal.l.verma@intel.com, jmorris@namei.org, ying.huang@intel.com, bp@suse.de, thomas.lendacky@amd.com, Pavel Tatashin , marc.zyngier@arm.com, jglisse@redhat.com, rppt@linux.vnet.ibm.com, bhelgaas@google.com, dan.j.williams@intel.com, linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org, sboyd@kernel.org, linux-kernel@vger.kernel.org, james.morse@arm.com, andrew.murray@arm.com, akpm@linux-foundation.org, fengguang.wu@intel.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu 25-04-19 16:31:38, Will Deacon wrote: > On Thu, Apr 25, 2019 at 05:25:50PM +0200, Michal Hocko wrote: > > On Tue 23-04-19 16:38:43, Pavel Tatashin wrote: > > > sparsemem section size determines the maximum size and alignment that > > > is allowed to offline/online memory block. The bigger the size the less > > > the clutter in /sys/devices/system/memory/*. On the other hand, however, > > > there is less flexability in what granules of memory can be added and > > > removed. > > > > > > Recently, it was enabled in Linux to hotadd persistent memory that > > > can be either real NV device, or reserved from regular System RAM > > > and has identity of devdax. > > > > > > The problem is that because ARM64's section size is 1G, and devdax must > > > have 2M label section, the first 1G is always missed when device is > > > attached, because it is not 1G aligned. > > > > > > Allow, better flexibility by making section size configurable. > > > > Is there any inherent reason (64k page size?) that enforces such a large > > memsection? > > I gave *vague* memories of running out of bits in the page flags if we > changed this, but that was a while back. If that's no longer the case, > then I'm open to changing the value, but I really don't want to expose > it as a Kconfig option as proposed in this patch. People won't have a > clue what to set and it doesn't help at all with the single-Image effort. Ohh, I absolutely agree about the config option part JFTR. 1GB section loos quite excessive. I am not really sure a standard arm64 memory layout looks though. -- Michal Hocko SUSE Labs _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel