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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 3176FC10F13 for ; Tue, 16 Apr 2019 09:16:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0ACD220675 for ; Tue, 16 Apr 2019 09:16:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726770AbfDPJQe (ORCPT ); Tue, 16 Apr 2019 05:16:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:36786 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726208AbfDPJQe (ORCPT ); Tue, 16 Apr 2019 05:16:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8CC82AE1D for ; Tue, 16 Apr 2019 09:16:33 +0000 (UTC) Date: Tue, 16 Apr 2019 11:16:33 +0200 From: Johannes Thumshirn To: dsterba@suse.cz, David Sterba , Linux BTRFS Mailinglist Subject: Re: [PATCH] btrfs: simplify read_extent_buffer_pages a bit Message-ID: <20190416091632.GA4226@linux-x5ow.site> References: <20190411164059.4981-1-jthumshirn@suse.de> <20190411165935.GA3476@twin.jikos.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190411165935.GA3476@twin.jikos.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Apr 11, 2019 at 06:59:35PM +0200, David Sterba wrote: > On Thu, Apr 11, 2019 at 06:40:59PM +0200, Johannes Thumshirn wrote: > > Currently read_extent_buffer_pages() uses a 4 pass algorithm to read an > > extent buffer's pages from disk, all 4 stages looping over all pages of > > the extent buffer. > > > > 1) Loop over all pages and lock them. > > 2) Loop over all pages and see if one is not marked as PageUptodate, so we > > can break out of the function early. > > 3) Loop over all pages and if the page is !PageUptodate read the page, > > otherwise unlock the page. > > 4) Loop over all pages and wait for stable pages. > > > > Unify the 1st two for loops, we can count the number of uptodate pages > > after we have locked them without the need for re-starting the loop. > > Effectively reverting 2571e739677f1e4c0c63f5ed49adcc0857923625 that > fixed a bug. Please have a look if something has really changed so that > the split loops are no longer necessary. After starring at the .s and .lst files GCC produces I cannot say whether this holds true or not. But as it was fixing a bug back then, I'll take back this patch. -- Johannes Thumshirn SUSE Labs Filesystems jthumshirn@suse.de +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850