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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 E2FC9C433E6 for ; Thu, 21 Jan 2021 16:53:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9682823A58 for ; Thu, 21 Jan 2021 16:53:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729527AbhAUPy4 (ORCPT ); Thu, 21 Jan 2021 10:54:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:52040 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727976AbhAUPwm (ORCPT ); Thu, 21 Jan 2021 10:52:42 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3A3B822DFA; Thu, 21 Jan 2021 15:51:42 +0000 (UTC) Date: Thu, 21 Jan 2021 15:51:39 +0000 From: Catalin Marinas To: Sudarshan Rajagopalan Cc: 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: <20210121155139.GG21811@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: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 20, 2021 at 09:29:13PM -0800, Sudarshan Rajagopalan wrote: > memory_block_size_bytes() determines the memory hotplug granularity i.e the > amount of memory which can be hot added or hot removed from the kernel. The > generic value here being MIN_MEMORY_BLOCK_SIZE (1UL << SECTION_SIZE_BITS) > for memory_block_size_bytes() on platforms like arm64 that does not override. > > Current SECTION_SIZE_BITS is 30 i.e 1GB which is large and a reduction here > increases memory hotplug granularity, thus improving its agility. A reduced > section size also reduces memory wastage in vmemmmap mapping for sections > with large memory holes. So we try to set the least section size as possible. > > A section size bits selection must follow: > (MAX_ORDER - 1 + PAGE_SHIFT) <= SECTION_SIZE_BITS > > CONFIG_FORCE_MAX_ZONEORDER is always defined on arm64 and so just following it > would help achieve the smallest section size. > > SECTION_SIZE_BITS = (CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT) > > SECTION_SIZE_BITS = 22 (11 - 1 + 12) i.e 4MB for 4K pages > SECTION_SIZE_BITS = 24 (11 - 1 + 14) i.e 16MB for 16K pages without THP > SECTION_SIZE_BITS = 25 (12 - 1 + 14) i.e 32MB for 16K pages with THP > SECTION_SIZE_BITS = 26 (11 - 1 + 16) i.e 64MB for 64K pages without THP > SECTION_SIZE_BITS = 29 (14 - 1 + 16) i.e 512MB for 64K pages with THP > > 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. > > Given these constraints, lets just reduce the section size to 128MB for 4K > and 16K base page size configs, and to 512MB for 64K base page size config. > > Signed-off-by: Sudarshan Rajagopalan > Suggested-by: Anshuman Khandual > Suggested-by: David Hildenbrand > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Anshuman Khandual > Cc: David Hildenbrand > Cc: Mike Rapoport > Cc: Mark Rutland > Cc: Logan Gunthorpe > Cc: Andrew Morton > Cc: Steven Price > Cc: Suren Baghdasaryan Reviewed-by: Catalin Marinas 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=-10.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 DA2B0C433DB for ; Thu, 21 Jan 2021 15:53:13 +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 8A9E822C9F for ; Thu, 21 Jan 2021 15:53:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8A9E822C9F 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=xoFh71yEhrsVrjTzD7t7UaUo6v/FUPRVYnd+pXtNfwM=; b=Elkpt9kH+85qXeGxAuorOnG3X m6E37n+Mz/17hfKpSYRVky4KeLlM17S6GyN2sirRqSiHBvbsTERs1orn75RIKJZVP5Dv6txfq2PX0 vOBmmBvkZ49/ayItlmDV9tpYa5Jbx0wq9SvKIWokEK23b6mt12Em57Dx79ICV8S/u8UHUahJ2ZV1R CG0CBEyDf6Ipeo29Jcf9R5Jq/+2hw/AVtRFJPf0HO2rmMUVDA4i9TM6TETtw4YuI5jyT/8eUcBc7N /JLAuEJhe5keszW0vJy46PYKXTJVoUBrGv7lcRqcYjq/fK51gN1a4DEY/+BTtSdur5+W39mF/j4pc /VggbZjXA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cFQ-00034h-LR; Thu, 21 Jan 2021 15:51:48 +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 1l2cFO-00033j-0J for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 15:51:47 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3A3B822DFA; Thu, 21 Jan 2021 15:51:42 +0000 (UTC) Date: Thu, 21 Jan 2021 15:51:39 +0000 From: Catalin Marinas To: Sudarshan Rajagopalan Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS Message-ID: <20210121155139.GG21811@gaia> References: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> 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_105146_132507_1FB49A33 X-CRM114-Status: GOOD ( 17.47 ) 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 , David Hildenbrand , Logan Gunthorpe , Anshuman Khandual , 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 Wed, Jan 20, 2021 at 09:29:13PM -0800, Sudarshan Rajagopalan wrote: > memory_block_size_bytes() determines the memory hotplug granularity i.e the > amount of memory which can be hot added or hot removed from the kernel. The > generic value here being MIN_MEMORY_BLOCK_SIZE (1UL << SECTION_SIZE_BITS) > for memory_block_size_bytes() on platforms like arm64 that does not override. > > Current SECTION_SIZE_BITS is 30 i.e 1GB which is large and a reduction here > increases memory hotplug granularity, thus improving its agility. A reduced > section size also reduces memory wastage in vmemmmap mapping for sections > with large memory holes. So we try to set the least section size as possible. > > A section size bits selection must follow: > (MAX_ORDER - 1 + PAGE_SHIFT) <= SECTION_SIZE_BITS > > CONFIG_FORCE_MAX_ZONEORDER is always defined on arm64 and so just following it > would help achieve the smallest section size. > > SECTION_SIZE_BITS = (CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT) > > SECTION_SIZE_BITS = 22 (11 - 1 + 12) i.e 4MB for 4K pages > SECTION_SIZE_BITS = 24 (11 - 1 + 14) i.e 16MB for 16K pages without THP > SECTION_SIZE_BITS = 25 (12 - 1 + 14) i.e 32MB for 16K pages with THP > SECTION_SIZE_BITS = 26 (11 - 1 + 16) i.e 64MB for 64K pages without THP > SECTION_SIZE_BITS = 29 (14 - 1 + 16) i.e 512MB for 64K pages with THP > > 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. > > Given these constraints, lets just reduce the section size to 128MB for 4K > and 16K base page size configs, and to 512MB for 64K base page size config. > > Signed-off-by: Sudarshan Rajagopalan > Suggested-by: Anshuman Khandual > Suggested-by: David Hildenbrand > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Anshuman Khandual > Cc: David Hildenbrand > Cc: Mike Rapoport > Cc: Mark Rutland > Cc: Logan Gunthorpe > Cc: Andrew Morton > Cc: Steven Price > Cc: Suren Baghdasaryan Reviewed-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel