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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 8B160CA9EC5 for ; Wed, 30 Oct 2019 14:02:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 59F0C20856 for ; Wed, 30 Oct 2019 14:02:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59F0C20856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=axis.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 048736B000A; Wed, 30 Oct 2019 10:02:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F3B256B000C; Wed, 30 Oct 2019 10:02:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E2A266B000D; Wed, 30 Oct 2019 10:02:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0107.hostedemail.com [216.40.44.107]) by kanga.kvack.org (Postfix) with ESMTP id C10CC6B000A for ; Wed, 30 Oct 2019 10:02:26 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 6361487C6 for ; Wed, 30 Oct 2019 14:02:26 +0000 (UTC) X-FDA: 76100615892.01.9CEB8BD Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 478AA1801BB6D for ; Wed, 30 Oct 2019 14:02:26 +0000 (UTC) X-HE-Tag: rifle24_151375735152c X-Filterd-Recvd-Size: 2655 Received: from smtp2.axis.com (smtp2.axis.com [195.60.68.18]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Wed, 30 Oct 2019 14:02:24 +0000 (UTC) IronPort-SDR: A6r/sRAgNcgUX6PPp549V7VnqRa+RPsV8Fgd5Ru+gJt5wm1+/Sadm+GxmQVl2XjiGjx+G3z7YQ XTVBPDQVArlEmWjORPnItJ6Lae0eZOWyNcIg1u5SF2X7bETQvczeZ/LzWt02wZ3DXAK3+tG9Ti dLDTINRcTZjDYjo76olwlpc8ZIKyxMkbc6m37TnfYz/ZIO5Ai0GClfE9RElV/B6zjTCAlUkKoZ 3M+ungPUzRNzzcmBJgVdCqPpATxq6sZ9436l2dLaNlfn+Fza0GiP+L8HKNtz+u7aUcy0cTcnqa nNI= X-IronPort-AV: E=Sophos;i="5.68,247,1569276000"; d="scan'208";a="1925617" X-Axis-User: NO X-Axis-NonUser: YES X-Virus-Scanned: Debian amavisd-new at bes.se.axis.com Date: Wed, 30 Oct 2019 15:02:16 +0100 From: Vincent Whitchurch To: Michal Hocko Cc: "akpm@linux-foundation.org" , "osalvador@suse.de" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] mm/sparse: Consistently do not zero memmap Message-ID: <20191030140216.i26n22asgafckfxy@axis.com> References: <20191030131122.8256-1-vincent.whitchurch@axis.com> <20191030132958.GD31513@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191030132958.GD31513@dhcp22.suse.cz> User-Agent: NeoMutt/20170113 (1.7.2) X-TM-AS-GCONF: 00 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 30, 2019 at 02:29:58PM +0100, Michal Hocko wrote: > On Wed 30-10-19 14:11:22, Vincent Whitchurch wrote: > > (I noticed this because on my ARM64 platform, with 1 GiB of memory the > > first [and only] section is allocated from the zeroing path while with > > 2 GiB of memory the first 1 GiB section is allocated from the > > non-zeroing path.) > > Do I get it right that sparse_buffer_init couldn't allocate memmap for > the full node for some reason and so sparse_init_nid would have to > allocate one for each memory section? Not quite. The sparsemap_buf is successfully allocated with the correct size in sparse_buffer_init(), but sparse_buffer_alloc() fails to allocate the same size from it. The reason it fails is that sparse_buffer_alloc() for some reason wants to return a pointer which is aligned to the allocation size. But the sparsemap_buf was only allocated with PAGE_SIZE alignment so there's not enough space to align it. I don't understand the reason for this alignment requirement since the fallback path also allocates with PAGE_SIZE alignment. I'm guessing the alignment is for the VMEMAP code which also uses sparse_buffer_alloc()?