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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 D73D4C433E0 for ; Thu, 21 Jan 2021 13:55:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BB9F233F8 for ; Thu, 21 Jan 2021 13:55:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728568AbhAUNzh (ORCPT ); Thu, 21 Jan 2021 08:55:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52150 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729707AbhAUNq7 (ORCPT ); Thu, 21 Jan 2021 08:46:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611236732; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vEf/VNdPwyHzK4KCLsMcGYA6UHSFxyACQQAos9koldw=; b=iEPurRIZMebBbcotBoCJEmDJLk4qadw6gsBu2fW9dYrpKye9Mdv6Nc+bgqyqrEJMbUPv/u eFXrl4rHU47dpfHKksjG6csxl4lmjXgua+2H8Bpzi3WMdNq2064NK4MHwyiai5zwAGu5p0 QIvzFbWjydwoVXAakFyaAohuCbrokbE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-555-ZvOMgdSdMHCcFKdAIM3I9w-1; Thu, 21 Jan 2021 08:45:30 -0500 X-MC-Unique: ZvOMgdSdMHCcFKdAIM3I9w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D5319800D55; Thu, 21 Jan 2021 13:45:27 +0000 (UTC) Received: from [10.36.115.70] (ovpn-115-70.ams2.redhat.com [10.36.115.70]) by smtp.corp.redhat.com (Postfix) with ESMTP id E3C8319CAC; Thu, 21 Jan 2021 13:45:24 +0000 (UTC) Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS To: Sudarshan Rajagopalan , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Anshuman Khandual Cc: Mike Rapoport , Mark Rutland , Logan Gunthorpe , Andrew Morton , Steven Price , Suren Baghdasaryan References: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 21 Jan 2021 14:45:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21.01.21 06:29, 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 > --- > arch/arm64/include/asm/sparsemem.h | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/sparsemem.h b/arch/arm64/include/asm/sparsemem.h > index 1f43fcc79738..eb4a75d720ed 100644 > --- a/arch/arm64/include/asm/sparsemem.h > +++ b/arch/arm64/include/asm/sparsemem.h > @@ -7,7 +7,26 @@ > > #ifdef CONFIG_SPARSEMEM > #define MAX_PHYSMEM_BITS CONFIG_ARM64_PA_BITS > -#define SECTION_SIZE_BITS 30 > -#endif > + > +/* > + * Section size must be at least 512MB for 64K base > + * page size config. Otherwise it will be less than > + * (MAX_ORDER - 1) and the build process will fail. > + */ > +#ifdef CONFIG_ARM64_64K_PAGES > +#define SECTION_SIZE_BITS 29 > + > +#else > + > +/* > + * Section size must be at least 128MB for 4K base > + * page size config. Otherwise PMD based huge page > + * entries could not be created for vmemmap mappings. > + * 16K follows 4K for simplicity. > + */ > +#define SECTION_SIZE_BITS 27 > +#endif /* CONFIG_ARM64_64K_PAGES */ > + > +#endif /* CONFIG_SPARSEMEM*/ > > #endif > I'm happy to see this change. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb 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=-15.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 D33D8C433DB for ; Thu, 21 Jan 2021 13:47:23 +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 6CAA4239A4 for ; Thu, 21 Jan 2021 13:47:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CAA4239A4 Authentication-Results: mail.kernel.org; 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Thu, 21 Jan 2021 08:45:30 -0500 X-MC-Unique: ZvOMgdSdMHCcFKdAIM3I9w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D5319800D55; Thu, 21 Jan 2021 13:45:27 +0000 (UTC) Received: from [10.36.115.70] (ovpn-115-70.ams2.redhat.com [10.36.115.70]) by smtp.corp.redhat.com (Postfix) with ESMTP id E3C8319CAC; Thu, 21 Jan 2021 13:45:24 +0000 (UTC) Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS To: Sudarshan Rajagopalan , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Anshuman Khandual References: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 21 Jan 2021 14:45:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <43843c5e092bfe3ec4c41e3c8c78a7ee35b69bb0.1611206601.git.sudaraja@codeaurora.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_084535_959732_CEEE4E95 X-CRM114-Status: GOOD ( 28.70 ) 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 , Logan Gunthorpe , Steven Price , Andrew Morton , Mike Rapoport , Suren Baghdasaryan 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 21.01.21 06:29, 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 > --- > arch/arm64/include/asm/sparsemem.h | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/sparsemem.h b/arch/arm64/include/asm/sparsemem.h > index 1f43fcc79738..eb4a75d720ed 100644 > --- a/arch/arm64/include/asm/sparsemem.h > +++ b/arch/arm64/include/asm/sparsemem.h > @@ -7,7 +7,26 @@ > > #ifdef CONFIG_SPARSEMEM > #define MAX_PHYSMEM_BITS CONFIG_ARM64_PA_BITS > -#define SECTION_SIZE_BITS 30 > -#endif > + > +/* > + * Section size must be at least 512MB for 64K base > + * page size config. Otherwise it will be less than > + * (MAX_ORDER - 1) and the build process will fail. > + */ > +#ifdef CONFIG_ARM64_64K_PAGES > +#define SECTION_SIZE_BITS 29 > + > +#else > + > +/* > + * Section size must be at least 128MB for 4K base > + * page size config. Otherwise PMD based huge page > + * entries could not be created for vmemmap mappings. > + * 16K follows 4K for simplicity. > + */ > +#define SECTION_SIZE_BITS 27 > +#endif /* CONFIG_ARM64_64K_PAGES */ > + > +#endif /* CONFIG_SPARSEMEM*/ > > #endif > I'm happy to see this change. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel