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=-5.3 required=3.0 tests=BAYES_00, 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 AF8C5C433DB for ; Thu, 21 Jan 2021 10:08:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 193E5239E4 for ; Thu, 21 Jan 2021 10:08:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 193E5239E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3EA3E6B0005; Thu, 21 Jan 2021 05:08:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 373BB6B0007; Thu, 21 Jan 2021 05:08:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23C856B0008; Thu, 21 Jan 2021 05:08:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0102.hostedemail.com [216.40.44.102]) by kanga.kvack.org (Postfix) with ESMTP id 089EF6B0005 for ; Thu, 21 Jan 2021 05:08:19 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B3DC4180AD81D for ; Thu, 21 Jan 2021 10:08:18 +0000 (UTC) X-FDA: 77729357076.07.cent18_0d0de4327562 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 96FED1803F9BE for ; Thu, 21 Jan 2021 10:08:18 +0000 (UTC) X-HE-Tag: cent18_0d0de4327562 X-Filterd-Recvd-Size: 2253 Received: from gentwo.org (gentwo.org [3.19.106.255]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Thu, 21 Jan 2021 10:08:18 +0000 (UTC) Received: by gentwo.org (Postfix, from userid 1002) id A245C3F04E; Thu, 21 Jan 2021 10:08:17 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id A030D3EFF6; Thu, 21 Jan 2021 10:08:17 +0000 (UTC) Date: Thu, 21 Jan 2021 10:08:17 +0000 (UTC) From: Christoph Lameter X-X-Sender: cl@www.lameter.com To: Sudarshan Rajagopalan cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Anshuman Khandual , David Hildenbrand , Mike Rapoport , Mark Rutland , Logan Gunthorpe , Andrew Morton , Steven Price , Suren Baghdasaryan Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS In-Reply-To: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> Message-ID: References: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 20 Jan 2021, Sudarshan Rajagopalan wrote: > But there are other problems in reducing SECTION_SIZE_BIT. Reducing it by too > much would over populate /sys/devices/system/memory/ and also consume too many > page->flags bits in the !vmemmap case. Also section size needs to be multiple > of 128MB to have PMD based vmemmap mapping with CONFIG_ARM64_4K_PAGES. There is also the issue of requiring more space in the TLB cache with smaller page sizes. Or does ARM resolve these into smaller TLB entries anyways (going on my x86 kwon how here)? Anyways if there are only a few TLB entries then the effect could be significant.