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=-9.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C80D7C4727E for ; Thu, 1 Oct 2020 19:51:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89D9720780 for ; Thu, 1 Oct 2020 19:51:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="i0X7xV+q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730171AbgJATvx (ORCPT ); Thu, 1 Oct 2020 15:51:53 -0400 Received: from z5.mailgun.us ([104.130.96.5]:35375 "EHLO z5.mailgun.us" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726671AbgJATvx (ORCPT ); Thu, 1 Oct 2020 15:51:53 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1601581913; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=q1wY2p0rUtdwprAqpqKnal9AO5BAuts9QPzd0435wBY=; b=i0X7xV+qg1xjwFHS90qxg1qpbJoBPFVZOf32rC9xNUMB4dpu3Y8Ep/Y+SfLo1My+NgQ1nUsq EF8L4By6jV4+zVAoFUPB3R0jkLUmW/fAzsWciw0vUCZDY6/45fZbM92z5Y+4GDrnSG4bZItU 3wuuNGX3gTSJqouLuYJXhirJd3c= X-Mailgun-Sending-Ip: 104.130.96.5 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n06.prod.us-west-2.postgun.com with SMTP id 5f76332ece84f363c7574377 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 01 Oct 2020 19:51:10 GMT Sender: sudaraja=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 62451C433F1; Thu, 1 Oct 2020 19:51:10 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: sudaraja) by smtp.codeaurora.org (Postfix) with ESMTPSA id 5B333C433CA; Thu, 1 Oct 2020 19:51:09 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 01 Oct 2020 12:51:09 -0700 From: Sudarshan Rajagopalan To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Mark Rutland , Logan Gunthorpe , David Hildenbrand , Andrew Morton , Steven Price Subject: Re: [PATCH v2] arm64/mm: add fallback option to allocate virtually contiguous memory In-Reply-To: References: Message-ID: <8201828cdd82e9c18588c95e7bdda59f@codeaurora.org> X-Sender: sudaraja@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-09-30 17:30, Anshuman Khandual wrote: > On 10/01/2020 04:43 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 | 14 ++++++++++++-- >> 1 file changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 75df62f..9edbbb8 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1121,8 +1121,18 @@ 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) { >> + if (altmap) >> + return -ENOMEM; /* no fallback */ > > Why ? If huge pages inside a vmemmap section might have been allocated > from altmap, the base page could also fallback on altmap. If this patch > has just followed the existing x86 semantics, it was written [1] long > back before vmemmap_populate_basepages() supported altmap allocation. > While adding that support [2] recently, it was deliberate not to change > x86 semantics as it was a platform decision. Nonetheless, it makes > sense > to fallback on altmap bases pages if and when required. > > [1] 4b94ffdc4163 (x86, mm: introduce vmem_altmap to augment > vmemmap_populate()) > [2] 1d9cfee7535c (mm/sparsemem: enable vmem_altmap support in > vmemmap_populate_basepages()) Yes agreed. We can allow fallback on altmap as well. I did indeed follow x86 semantics. Will send the updated patch. Sudarshan -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project