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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 8E563C43460 for ; Wed, 5 May 2021 15:08:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 635B861176 for ; Wed, 5 May 2021 15:08:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233054AbhEEPI4 (ORCPT ); Wed, 5 May 2021 11:08:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46724 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232192AbhEEPIy (ORCPT ); Wed, 5 May 2021 11:08:54 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDF5DC061574; Wed, 5 May 2021 08:07:57 -0700 (PDT) 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: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=hBpQR/0D3JnfgszdRdi1IhKjYmrqMJy8CCih3IT3ePo=; b=qIlhenN55SYdUaLUwpXFQa4Lvx AlZiLLKgmBfGYEWkIFBMaOP2k5v1vfs4hmxqE0t6FsWrQ+gLV8EJB2+BIU+v2KfG1lJbV8gD1nwlN pKb/Hd3S27b4Dqxvy4W+ag4ORb/7eDpFBjGUuBv4FKRBH1/Zwjr1UFvHBIyrMpzEWYOFc1GY5cPaf 7UFQIg+KdcYaxXFvZquza5EA/IINkXOIQqsI4Rq8qS5XzmeZOry5pM6aEyTxH375R8/AjZcSW55lu OD+U0dSdIgOPxZDBiOazq5WROJ5dZ4EfgtA9u2KzVWa0F3XTq3krZUuNlFhnlMZkOOfuMmHFO+POK P3N3vy/A==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1leJ6x-000T5S-7E; Wed, 05 May 2021 15:06:54 +0000 From: "Matthew Wilcox (Oracle)" To: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: "Matthew Wilcox (Oracle)" , linux-kernel@vger.kernel.org, Christoph Hellwig , David Hildenbrand , Zi Yan Subject: [PATCH v9 01/96] mm: Optimise nth_page for contiguous memmap Date: Wed, 5 May 2021 16:04:53 +0100 Message-Id: <20210505150628.111735-2-willy@infradead.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210505150628.111735-1-willy@infradead.org> References: <20210505150628.111735-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) -- 2.30.2