From patchwork Tue Apr 13 19:46:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 12201355 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=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 1BF4DC433ED for ; Tue, 13 Apr 2021 19:46:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 77CAB613C6 for ; Tue, 13 Apr 2021 19:46:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 77CAB613C6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BA9F96B006E; Tue, 13 Apr 2021 15:46:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B33C26B0070; Tue, 13 Apr 2021 15:46:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9ACBE6B0071; Tue, 13 Apr 2021 15:46:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0244.hostedemail.com [216.40.44.244]) by kanga.kvack.org (Postfix) with ESMTP id 7E78B6B006E for ; Tue, 13 Apr 2021 15:46:52 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 2868F2DE1021 for ; Tue, 13 Apr 2021 19:46:52 +0000 (UTC) X-FDA: 78028376664.26.64B45B9 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf16.hostedemail.com (Postfix) with ESMTP id 8F5ED80192E5 for ; Tue, 13 Apr 2021 19:46:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:In-Reply-To:References; bh=oEFp9oGvZ6I7WinWmnB+A7S0Z09gh1JWVMa9yxM84sg=; b=bS9I+q7kiWT1NzIv1yWFEMXJF/ x/Syia9IoTE1ssQxeowX47W4cnMwsZB6TiG4bCkeSJcxmuLk5FF8X3Af7cleJsofkMRbhl+xXsCyJ 3IBD+ZysmU+c7sQX1dLQsN7JN/MWh1EAWsogqxB+XphexbQlaD4F0AhT8Fm5vaY6Y5DlBzhBeZGA+ 6vDWf81wn/a0/kFG36vbLbzlQZwBLCszP0yBQ9DQ+lb7MbFDfiHwkJVCHu6Q2WMz4UWeZIJHSW09+ B7zcjgDE1/UWpWuPkstt0ig2WmoUHwEzDEb7qP8QXILV2HHr29Ltlsw3oihSNPJ/Ag/6vXPuyYPqG xCalSiHA==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lWOzX-006BHL-16; Tue, 13 Apr 2021 19:46:33 +0000 From: "Matthew Wilcox (Oracle)" To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tejun Heo , FUJITA Tomonori , Douglas Gilbert , Chris Wilson Cc: "Matthew Wilcox (Oracle)" , Christoph Hellwig Subject: [PATCH] mm: Optimise nth_page for contiguous memmap Date: Tue, 13 Apr 2021 20:46:25 +0100 Message-Id: <20210413194625.1472345-1-willy@infradead.org> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 X-Stat-Signature: s9d48ogsd3tgo15yzz1izkbxdkqq6f3y X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8F5ED80192E5 Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618343210-612727 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: If the memmap is virtually contiguous (either because we're using a virtually mapped memmap or because we don't support a discontig memmap at all), then we can implement nth_page() by simple addition. Contrary to popular belief, the compiler is not able to optimise this itself for a vmemmap configuration. This reduces one example user (sg.c) by four instructions: struct page *page = nth_page(rsv_schp->pages[k], offset >> PAGE_SHIFT); before: 49 8b 45 70 mov 0x70(%r13),%rax 48 63 c9 movslq %ecx,%rcx 48 c1 eb 0c shr $0xc,%rbx 48 8b 04 c8 mov (%rax,%rcx,8),%rax 48 2b 05 00 00 00 00 sub 0x0(%rip),%rax R_X86_64_PC32 vmemmap_base-0x4 48 c1 f8 06 sar $0x6,%rax 48 01 d8 add %rbx,%rax 48 c1 e0 06 shl $0x6,%rax 48 03 05 00 00 00 00 add 0x0(%rip),%rax R_X86_64_PC32 vmemmap_base-0x4 after: 49 8b 45 70 mov 0x70(%r13),%rax 48 63 c9 movslq %ecx,%rcx 48 c1 eb 0c shr $0xc,%rbx 48 c1 e3 06 shl $0x6,%rbx 48 03 1c c8 add (%rax,%rcx,8),%rbx Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: David Hildenbrand Reviewed-by: Zi Yan --- include/linux/mm.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 25b9041f9925..2327f99b121f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -234,7 +234,11 @@ int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *, int __add_to_page_cache_locked(struct page *page, struct address_space *mapping, pgoff_t index, gfp_t gfp, void **shadowp); +#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n)) +#else +#define nth_page(page,n) ((page) + (n)) +#endif /* to align the pointer to the (next) page boundary */ #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)