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 B71CAC433E0 for ; Thu, 21 Jan 2021 15:54:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4619923A1D for ; Thu, 21 Jan 2021 15:54:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4619923A1D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BF72A6B0007; Thu, 21 Jan 2021 10:54:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BA6F36B0008; Thu, 21 Jan 2021 10:54:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ABDA66B000A; Thu, 21 Jan 2021 10:54:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0073.hostedemail.com [216.40.44.73]) by kanga.kvack.org (Postfix) with ESMTP id 965E66B0007 for ; Thu, 21 Jan 2021 10:54:17 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 615591DF3 for ; Thu, 21 Jan 2021 15:54:17 +0000 (UTC) X-FDA: 77730228954.08.van99_5f0f4ad27564 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 404A61819E76F for ; Thu, 21 Jan 2021 15:54:17 +0000 (UTC) X-HE-Tag: van99_5f0f4ad27564 X-Filterd-Recvd-Size: 2292 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Thu, 21 Jan 2021 15:54:16 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 25AE822C9F; Thu, 21 Jan 2021 15:54:12 +0000 (UTC) Date: Thu, 21 Jan 2021 15:54:10 +0000 From: Catalin Marinas To: Christoph Lameter Cc: Sudarshan Rajagopalan , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, 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 Message-ID: <20210121155410.GH21811@gaia> References: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu, Jan 21, 2021 at 10:08:17AM +0000, Christoph Lameter wrote: > 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. There is indeed more TLB pressure with smaller page sizes but this patch doesn't change this. -- Catalin