From patchwork Mon Oct 8 10:03:55 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Punit Agrawal X-Patchwork-Id: 10630333 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D0A2B14BD for ; Mon, 8 Oct 2018 10:04:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B669528AA4 for ; Mon, 8 Oct 2018 10:04:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A9F1E28C02; Mon, 8 Oct 2018 10:04:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 4A2B328AA4 for ; Mon, 8 Oct 2018 10:04:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=P9B0ctGt1ux3rlt60fkNAz1WO7XHvvcjqaaXbAq61+w=; b=MyYq+QeasYTm6hO/32WFzlZXEb fsOPOex5lTPp+Zs5rR4/vu2r0yxvEwoKCAMCcxSFskPeAr7E5CYP5mdCiuAIbI9MS49/iEePjEsML z3sLQTv7ka7ZEsTpzYStVA8vIPIQo1nz6V+AcSqmFiPuD1DqDs+17mz7gs0D1T2thq76wcUOLye89 aoppG9ztYQRj7Rp5glokkYYaX69RyuZk0T1GWaCjj0BGzdcM0siu8xaBEquFEbkhAy8SoF60YzTQm LOFGQdT7MG9H6jMfqrqptyxqyP0P36jfBKAVhhzugJLPqmm/ROKisWraWu8mVTxSl4jhrLtHFmxmU zcFGIe+A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1g9SOg-0005gE-Dj; Mon, 08 Oct 2018 10:04:18 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1g9SOd-0005fR-7c for linux-arm-kernel@lists.infradead.org; Mon, 08 Oct 2018 10:04:17 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D6EC57A9; Mon, 8 Oct 2018 03:04:04 -0700 (PDT) Received: from localhost (e105922-lin.cambridge.arm.com [10.1.197.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 578FA3F5D3; Mon, 8 Oct 2018 03:04:04 -0700 (PDT) From: Punit Agrawal To: linux-doc@vger.kernel.org Subject: [PATCH v2] Documentation/arm64: HugeTLB page implementation Date: Mon, 8 Oct 2018 11:03:55 +0100 Message-Id: <20181008100355.31820-1-punit.agrawal@arm.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <97e4e5fb-24ed-0545-414a-6a0c0116e6b8@infradead.org> References: <97e4e5fb-24ed-0545-414a-6a0c0116e6b8@infradead.org> X-ARM-No-Footer: FoSSMail X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181008_030415_309829_59100521 X-CRM114-Status: GOOD ( 14.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jonathan Corbet , rdunlap@infradead.org, steve.capper@arm.com, Catalin Marinas , Punit Agrawal , Will Deacon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Arm v8 architecture supports multiple page sizes - 4k, 16k and 64k. Based on the active page size, the Linux port supports corresponding hugepage sizes at PMD and PUD(4k only) levels. In addition, the architecture also supports caching larger sized ranges (composed of multiple entries) at the PTE and PMD level in the TLBs using the contiguous bit. The Linux port makes use of this architectural support to enable additional hugepage sizes. Describe the two different types of hugepages supported by the arm64 kernel and the hugepage sizes enabled by each. Signed-off-by: Punit Agrawal Cc: Catalin Marinas Cc: Will Deacon Cc: Jonathan Corbet Acked-by: Randy Dunlap Acked-by: Will Deacon --- Hi, This version incorporates the feedback on v1. Thanks, Punit Documentation/arm64/hugetlbpage.txt | 38 +++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 Documentation/arm64/hugetlbpage.txt diff --git a/Documentation/arm64/hugetlbpage.txt b/Documentation/arm64/hugetlbpage.txt new file mode 100644 index 000000000000..cfae87dc653b --- /dev/null +++ b/Documentation/arm64/hugetlbpage.txt @@ -0,0 +1,38 @@ +HugeTLBpage on ARM64 +==================== + +Hugepage relies on making efficient use of TLBs to improve performance of +address translations. The benefit depends on both - + + - the size of hugepages + - size of entries supported by the TLBs + +The ARM64 port supports two flavours of hugepages. + +1) Block mappings at the pud/pmd level +-------------------------------------- + +These are regular hugepages where a pmd or a pud page table entry points to a +block of memory. Regardless of the supported size of entries in TLB, block +mappings reduce the depth of page table walk needed to translate hugepage +addresses. + +2) Using the Contiguous bit +--------------------------- + +The architecture provides a contiguous bit in the translation table entries +(D4.5.3, ARM DDI 0487C.a) that hints to the MMU to indicate that it is one of a +contiguous set of entries that can be cached in a single TLB entry. + +The contiguous bit is used in Linux to increase the mapping size at the pmd and +pte (last) level. The number of supported contiguous entries varies by page size +and level of the page table. + + +The following hugepage sizes are supported - + + CONT PTE PMD CONT PMD PUD + -------- --- -------- --- + 4K: 64K 2M 32M 1G + 16K: 2M 32M 1G + 64K: 2M 512M 16G