From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:20458 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750788AbbKBBec (ORCPT ); Sun, 1 Nov 2015 20:34:32 -0500 Subject: Re: Regression in: [PATCH 4/4] btrfs: qgroup: account shared subtree during snapshot delete To: Stefan Priebe , "linux-btrfs@vger.kernel.org" , References: <56367AE8.9030509@profihost.ag> CC: , Chris Mason From: Qu Wenruo Message-ID: <5636BDA0.4020200@cn.fujitsu.com> Date: Mon, 2 Nov 2015 09:34:24 +0800 MIME-Version: 1.0 In-Reply-To: <56367AE8.9030509@profihost.ag> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Stefan Priebe wrote on 2015/11/01 21:49 +0100: > Hi, > > this one: http://www.spinics.net/lists/linux-btrfs/msg47377.html > > adds a regression to my test systems with very large disks (30tb and 50tb). > > btrfs balance is super slow afterwards while heavily making use of cp > --reflink=always on big files (200gb - 500gb). > > Sorry didn't know how to correctly reply to that "old" message. > > Greets, > Stefan > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Thanks for the testing. Are you using qgroup or just doing normal balance with qgroup disabled? For the latter case, that's should be optimized to skip the dirty extent insert in qgroup disabled case. For qgroup enabled case, I'm afraid that's the design. As relocation will drop a subtree to relocate, and to ensure qgroup consistent, we must walk down all the tree blocks and mark them dirty for later qgroup accounting. But there should be some hope left for optimization. For example, if all subtree blocks are already relocated, we can skip the tree down walk routine. Anyway, for your case of huge files, as tree level grows rapidly, any workload involving tree iteration will be very time consuming. Like snapshot deletion and relocation. BTW, thanks for you regression report, I also found another problem of the patch. I'll reply to the author to improve the patchset. Thanks, Qu