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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 23FA7C4363D for ; Tue, 6 Oct 2020 03:36:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C560B208A9 for ; Tue, 6 Oct 2020 03:36:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726875AbgJFDgz (ORCPT ); Mon, 5 Oct 2020 23:36:55 -0400 Received: from foss.arm.com ([217.140.110.172]:36820 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725917AbgJFDgz (ORCPT ); Mon, 5 Oct 2020 23:36:55 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7DDDB113E; Mon, 5 Oct 2020 20:36:54 -0700 (PDT) Received: from [10.163.74.99] (unknown [10.163.74.99]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7045B3F71F; Mon, 5 Oct 2020 20:36:51 -0700 (PDT) Subject: Re: [PATCH v3] arm64/mm: add fallback option to allocate virtually contiguous memory To: Sudarshan Rajagopalan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Logan Gunthorpe , David Hildenbrand , Andrew Morton , Steven Price References: <9e6178d2828e9c36275487263c5842c688e5b731.1601582954.git.sudaraja@codeaurora.org> From: Anshuman Khandual Message-ID: <49dd60a7-25f4-8dc1-b905-088dff2a84fb@arm.com> Date: Tue, 6 Oct 2020 09:06:20 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <9e6178d2828e9c36275487263c5842c688e5b731.1601582954.git.sudaraja@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/02/2020 01:46 AM, Sudarshan Rajagopalan wrote: > When section mappings are enabled, we allocate vmemmap pages from physically > continuous memory of size PMD_SIZE using vmemmap_alloc_block_buf(). Section > mappings are good to reduce TLB pressure. But when system is highly fragmented > and memory blocks are being hot-added at runtime, its possible that such > physically continuous memory allocations can fail. Rather than failing the > memory hot-add procedure, add a fallback option to allocate vmemmap pages from > discontinuous pages using vmemmap_populate_basepages(). > > Signed-off-by: Sudarshan Rajagopalan > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Anshuman Khandual > Cc: Mark Rutland > Cc: Logan Gunthorpe > Cc: David Hildenbrand > Cc: Andrew Morton > Cc: Steven Price > --- > arch/arm64/mm/mmu.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 75df62f..11f8639 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1121,8 +1121,15 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, > void *p = NULL; > > p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); > - if (!p) > - return -ENOMEM; > + if (!p) { > + /* > + * fallback allocating with virtually > + * contiguous memory for this section > + */ Mapping is always virtually contiguous with or without huge pages. Please drop this comment here, as it's obvious. > + if (vmemmap_populate_basepages(addr, next, node, NULL)) > + return -ENOMEM; Please send in the 'altmap' instead of NULL for allocation from device memory if and when requested.