From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp65.iad3a.emailsrvr.com ([173.203.187.65]:41316 "EHLO smtp65.iad3a.emailsrvr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbdCaHFZ (ORCPT ); Fri, 31 Mar 2017 03:05:25 -0400 Received: from smtp1.relay.iad3a.emailsrvr.com (localhost [127.0.0.1]) by smtp1.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 4935A5C16 for ; Fri, 31 Mar 2017 03:05:23 -0400 (EDT) Received: by smtp1.relay.iad3a.emailsrvr.com (Authenticated sender: m.khalili-AT-rqc.ru) with ESMTPSA id E51645B9A for ; Fri, 31 Mar 2017 03:05:22 -0400 (EDT) To: linux-btrfs@vger.kernel.org From: Marat Khalili Subject: Do different btrfs volumes compete for CPU? Message-ID: <43a14754-1047-552e-78a9-6503dfc0d121@rqc.ru> Date: Fri, 31 Mar 2017 10:05:20 +0300 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Approximately 16 hours ago I've run a script that deleted >~100 snapshots and started quota rescan on a large USB-connected btrfs volume (5.4 of 22 TB occupied now). Quota rescan only completed just now, with 100% load from [btrfs-transacti] throughout this period, which is probably ~ok depending on your view on things. What worries me is innocent process using _another_, SATA-connected btrfs volume that hung right after I started my script and took >30 minutes to be sigkilled. There's nothing interesting in the kernel log, and attempts to attach strace to the process output nothing, but I of course suspect that it freezed on disk operation. I wonder: 1) Can there be a contention for CPU or some mutexes between kernel btrfs threads belonging to different volumes? 2) If yes, can anything be done about it other than mounting volumes from (different) VMs? > $ uname -a; btrfs --version > Linux host 4.4.0-66-generic #87-Ubuntu SMP Fri Mar 3 15:29:05 UTC 2017 > x86_64 x86_64 x86_64 GNU/Linux > btrfs-progs v4.4 -- With Best Regards, Marat Khalili