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 BEF26C433DB for ; Thu, 21 Jan 2021 15:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 809E723A1D for ; Thu, 21 Jan 2021 15:57:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731895AbhAUP5P (ORCPT ); Thu, 21 Jan 2021 10:57:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:52522 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729541AbhAUPzK (ORCPT ); Thu, 21 Jan 2021 10:55:10 -0500 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) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 419C3C433DB for ; Thu, 21 Jan 2021 15:55:38 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E5DA122C9F for ; Thu, 21 Jan 2021 15:55:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E5DA122C9F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MYIiVGKmoapUMPqHuHFvEwjyfb4Z7Tm/k+CwDhMf2fg=; b=GbwES9bUEeYRCRZyNiHKkVv9b S8os4QDUuoOgbeWfkrJjxuBPUV+ktvxl5bnM8Y3hGzF1UZSQFXMSzXGmII1Juaq08Wteem8MgtKH5 CEAFO2RB8tpit44ilDedfOyOvtbhMHx+ap48mBw51XtQIwnfnSsqHF0wVD44SHsEpgV1OuOWomuiy jYO8erwQSJVupLNVaqMMvWl+4pZue4shN3gRc6F+Wtd0byUfmVJ0NsyiGLAtaQtWBhsfIv1N3WZ2u 0zczrHG6f7Qb+CammssHFD0U822ICVoWCaniacG3TOvCD+uzh4MH/gx47B37AMypbY4v7w99oBdYh FA+9rbzEw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cHr-0003mc-Cd; Thu, 21 Jan 2021 15:54:19 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cHo-0003lD-DQ for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 15:54:17 +0000 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 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-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_105416_527835_917132A9 X-CRM114-Status: GOOD ( 14.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Anshuman Khandual , Logan Gunthorpe , Sudarshan Rajagopalan , David Hildenbrand , linux-kernel@vger.kernel.org, Mike Rapoport , Suren Baghdasaryan , linux-mm@kvack.org, Andrew Morton , Steven Price , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel