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=-3.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 A6E16C4332D for ; Fri, 20 Mar 2020 18:41:51 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 55DF720739 for ; Fri, 20 Mar 2020 18:41:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="wi2vuW5I" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55DF720739 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48kXgK39PDzF0c1 for ; Sat, 21 Mar 2020 05:41:49 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=ebiggers@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=default header.b=wi2vuW5I; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48kXf65BMWzF0ZD for ; Sat, 21 Mar 2020 05:40:46 +1100 (AEDT) Received: from sol.localdomain (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 275D420739; Fri, 20 Mar 2020 18:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584729643; bh=0lySpfIbLYVkl86wERt9XwrjnUjq7J+z8XZeuge/+7s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wi2vuW5Igyu46y5Wx05mkvW8a/VLckiN7s/9GNIOdxM9U7yQM1pyY2njL/QMwkPan KWQEARrCqs16OuxD5B6Kg1R9790qkHmt4v/O/PZizCk3+z+HWCmu6og3Em53508k9B iW3Hml7aQ3jDLnTGNz1ZqdOb+OAH89RjMJ2Qz1nU= Date: Fri, 20 Mar 2020 11:40:41 -0700 From: Eric Biggers To: Matthew Wilcox Subject: Re: [PATCH v9 20/25] ext4: Convert from readpages to readahead Message-ID: <20200320184041.GG851@sol.localdomain> References: <20200320142231.2402-1-willy@infradead.org> <20200320142231.2402-21-willy@infradead.org> <20200320173734.GD851@sol.localdomain> <20200320174848.GC4971@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200320174848.GC4971@bombadil.infradead.org> X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: cluster-devel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, William Kucharski , linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, ocfs2-devel@oss.oracle.com Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" On Fri, Mar 20, 2020 at 10:48:48AM -0700, Matthew Wilcox wrote: > 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. Yeah, it does look like the list_del() made the prefetchw() useless, so it should just be removed. The prefetchw() dates all the way back to mpage_readpages() being added in 2002, but even then the list_del() was immediately afterwards, and 'flags' and 'lru' were in the same cache line in 'struct page' even then (assuming at least a 32-byte cache line size), so... - Eric