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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89175C433EF for ; Wed, 27 Apr 2022 04:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243393AbiD0EWv (ORCPT ); Wed, 27 Apr 2022 00:22:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232216AbiD0EWu (ORCPT ); Wed, 27 Apr 2022 00:22:50 -0400 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D30B415377E for ; Tue, 26 Apr 2022 21:19:40 -0700 (PDT) Received: from dread.disaster.area (pa49-195-62-197.pa.nsw.optusnet.com.au [49.195.62.197]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 08DB0537AFA; Wed, 27 Apr 2022 14:19:39 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1njZ9N-0050zP-Mn; Wed, 27 Apr 2022 14:19:37 +1000 Date: Wed, 27 Apr 2022 14:19:37 +1000 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 3/4] xfs: speed up rmap lookups by using non-overlapped lookups when possible Message-ID: <20220427041937.GE1098723@dread.disaster.area> References: <165102068549.3922526.15959517253241370597.stgit@magnolia> <165102070261.3922526.1584531429524068308.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <165102070261.3922526.1584531429524068308.stgit@magnolia> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=VuxAv86n c=1 sm=1 tr=0 ts=6268c45c a=KhGSFSjofVlN3/cgq4AT7A==:117 a=KhGSFSjofVlN3/cgq4AT7A==:17 a=kj9zAlcOel0A:10 a=z0gMJWrwH1QA:10 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=7-415B0cAAAA:8 a=NcgjJLDl60GzauDnsn8A:9 a=CjuIK1q_8ugA:10 a=AjGcO6oz07-iQ99wixmX:22 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Apr 26, 2022 at 05:51:42PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong > > Reverse mapping on a reflink-capable filesystem has some pretty high > overhead when performing file operations. This is because the rmap > records for logically and physically adjacent extents might not be > adjacent in the rmap index due to data block sharing. As a result, we > use expensive overlapped-interval btree search, which walks every record > that overlaps with the supplied key in the hopes of finding the record. > > However, profiling data shows that when the index contains a record that > is an exact match for a query key, the non-overlapped btree search > function can find the record much faster than the overlapped version. > Try the non-overlapped lookup first, which will make scrub run much > faster. > > Signed-off-by: Darrick J. Wong LGTM. Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com