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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 E5670C4332D for ; Fri, 20 Mar 2020 17:48:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C15DD2072C for ; Fri, 20 Mar 2020 17:48:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="h1Kzauch" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727141AbgCTRsu (ORCPT ); Fri, 20 Mar 2020 13:48:50 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51296 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgCTRsu (ORCPT ); Fri, 20 Mar 2020 13:48:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=REJDSQBSjlxGvUa9yFvVpoZkbE4uGtyMxtUffkDr/yg=; b=h1KzauchMVn1GcHidDQlLm4NDv aK4kqaKyat0c5S0apNaFmVi2M8lBpKqc6HcaPGEx+FFNw4NjYR32w5n0WAiLlaQiNyEfedB+7qoTL E/THmbYmMV4oouS6HA97h/6mPTqu5anVComDHxmPW4cHFSSyakaX+gQtXZhMNNfMHvVSjwaoJ0h2L OUdg+DUV4zfIM1jYNB9gSyndXuMPQpPpoePO6Xnc1zLjP/inzuV8mvsbNGEKjizrXkCo/5ONaqRd7 SqjRvCtsua+M1JEUo9eCXIRJNJsizFMS59zha5v/io1cPAKUeptHjpuXzj4A/3UtnQK12YL/XylLS RApjCAiA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jFLlI-0000w5-Ps; Fri, 20 Mar 2020 17:48:48 +0000 Date: Fri, 20 Mar 2020 10:48:48 -0700 From: Matthew Wilcox To: Eric Biggers Cc: Andrew Morton , linux-xfs@vger.kernel.org, William Kucharski , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Subject: Re: [PATCH v9 20/25] ext4: Convert from readpages to readahead Message-ID: <20200320174848.GC4971@bombadil.infradead.org> References: <20200320142231.2402-1-willy@infradead.org> <20200320142231.2402-21-willy@infradead.org> <20200320173734.GD851@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200320173734.GD851@sol.localdomain> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri, Mar 20, 2020 at 10:37:34AM -0700, Eric Biggers wrote: > On Fri, Mar 20, 2020 at 07:22:26AM -0700, Matthew Wilcox wrote: > > From: "Matthew Wilcox (Oracle)" > > > > Use the new readahead operation in ext4 > > > > Signed-off-by: Matthew Wilcox (Oracle) > > Reviewed-by: William Kucharski > > --- > > fs/ext4/ext4.h | 3 +-- > > fs/ext4/inode.c | 21 +++++++++------------ > > fs/ext4/readpage.c | 22 ++++++++-------------- > > 3 files changed, 18 insertions(+), 28 deletions(-) > > > > Reviewed-by: Eric Biggers > > > + if (rac) { > > + page = readahead_page(rac); > > prefetchw(&page->flags); > > - list_del(&page->lru); > > - if (add_to_page_cache_lru(page, mapping, page->index, > > - readahead_gfp_mask(mapping))) > > - goto next_page; > > } > > Maybe the prefetchw(&page->flags) should be included in readahead_page()? > Most of the callers do it. I did notice that a lot of callers do that. I wonder whether it (still) helps or whether it's just cargo-cult programming. It can't possibly have helped before because we did list_del(&page->lru) as the very next instruction after prefetchw(), and they're in the same cacheline. It'd be interesting to take it out and see what happens to performance.