From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 53B7E6B0003 for ; Thu, 5 Apr 2018 18:08:45 -0400 (EDT) Received: by mail-pl0-f69.google.com with SMTP id o2-v6so18399572plk.14 for ; Thu, 05 Apr 2018 15:08:45 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id s10si6088354pgc.129.2018.04.05.15.08.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Apr 2018 15:08:44 -0700 (PDT) Date: Thu, 5 Apr 2018 15:08:42 -0700 From: Andrew Morton Subject: Re: [PATCH v3 0/4] mm/sparse: Optimize memmap allocation during sparse_init() Message-Id: <20180405150842.350e4febc06a813138f00416@linux-foundation.org> In-Reply-To: <20180228032657.32385-1-bhe@redhat.com> References: <20180228032657.32385-1-bhe@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Baoquan He Cc: linux-kernel@vger.kernel.org, dave.hansen@intel.com, pagupta@redhat.com, linux-mm@kvack.org, kirill.shutemov@linux.intel.com On Wed, 28 Feb 2018 11:26:53 +0800 Baoquan He wrote: > This is v3 post. V1 can be found here: > https://www.spinics.net/lists/linux-mm/msg144486.html > > In sparse_init(), two temporary pointer arrays, usemap_map and map_map > are allocated with the size of NR_MEM_SECTIONS. They are used to store > each memory section's usemap and mem map if marked as present. In > 5-level paging mode, this will cost 512M memory though they will be > released at the end of sparse_init(). System with few memory, like > kdump kernel which usually only has about 256M, will fail to boot > because of allocation failure if CONFIG_X86_5LEVEL=y. > > In this patchset, optimize the memmap allocation code to only use > usemap_map and map_map with the size of nr_present_sections. This > makes kdump kernel boot up with normal crashkernel='' setting when > CONFIG_X86_5LEVEL=y. This patchset could do with some more review, please?