From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com ([192.55.52.88]:50573 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750844AbcBLGM2 (ORCPT ); Fri, 12 Feb 2016 01:12:28 -0500 From: Andi Kleen To: Premysl Kouril Cc: linux-fsdevel@vger.kernel.org Subject: Re: EXT4 vs LVM performance for VMs References: Date: Thu, 11 Feb 2016 22:12:19 -0800 In-Reply-To: (Premysl Kouril's message of "Thu, 11 Feb 2016 21:50:58 +0100") Message-ID: <87twlee9to.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Premysl Kouril writes: > > So basically we attribute the lower EXT4 performance to these points > where things need to be synchronized using locks but this is just what > we see at high level so I would be curious if dev community thinks > this might be the cause. Except for the last the backtraces you're showing are for futex locks, which are not used by the kernel, but some user process. So the locking problem is somewhere in the user space setup (perhaps in qemu). This would indicate your ext4 set up is not the same as LVM. The later is the inode mutex which is needed for POSIX semantics to get atomic writes. -Andi -- ak@linux.intel.com -- Speaking for myself only