From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.kundenserver.de ([217.72.192.74]:62394 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750882AbcCAFRi (ORCPT ); Tue, 1 Mar 2016 00:17:38 -0500 Received: from [10.60.11.138] ([63.163.107.100]) by mrelayeu.kundenserver.de (mreue103) with ESMTPSA (Nemesis) id 0MH5lK-1afYd620sk-00Dmnt for ; Tue, 01 Mar 2016 06:17:30 +0100 Message-ID: <56D525E1.6010407@vlnb.net> Date: Mon, 29 Feb 2016 21:17:21 -0800 From: Vladislav Bolkhovitin MIME-Version: 1.0 Subject: Fio high IOPS measurement mistake Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: fio@vger.kernel.org Hello, I'm currently looking at one NVRAM device, and during fio tests noticed that each fio thread consumes 30% of user space CPU. I'm using ioengine=libaio, buffered=0, sync=0 and direct=1, so user space CPU consumption should be virtually zero. That 30% user CPU consumption makes me suspect that this is overhead for internal fio housekeeping, i.e., scientifically speaking, fio instrumental measurement mistake (I hope, I'm using correct English terms). Can anybody comment it and suggest how to decrease this user space CPU consumption? Here is my full fio job: [global] ioengine=libaio buffered=0 sync=0 direct=1 randrepeat=1 softrandommap=1 rw=randread bs=4k filename=./nvram (it's a link to a block device) exitall=1 thread=1 disable_lat=1 disable_slat=1 disable_clat=1 loops=10 iodepth=16 [file1] [file2] I'm working on million+ IOPS range. Thanks, Vlad