From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mondschein.lichtvoll.de ([194.150.191.11]:53553 "EHLO mail.lichtvoll.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754590Ab1HCUub convert rfc822-to-8bit (ORCPT ); Wed, 3 Aug 2011 16:50:31 -0400 From: Martin Steigerwald Subject: Re: Measuring IOPS Date: Wed, 3 Aug 2011 22:50:29 +0200 References: <201107291737.40463.Martin@lichtvoll.de> <201108032242.16778.Martin@lichtvoll.de> (sfid-20110803_224834_033116_69EEA2DA) In-Reply-To: <201108032242.16778.Martin@lichtvoll.de> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message-Id: <201108032250.30096.Martin@lichtvoll.de> Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Jeff Moyer Cc: fio@vger.kernel.org Am Mittwoch, 3. August 2011 schrieb Martin Steigerwald: > Am Mittwoch, 3. August 2011 schrieben Sie: > > Martin Steigerwald writes: [...] > Does using iodepth > 1 need ioengine=3Dlibaio? Let=EF=BF=BDs see the manp= age: >=20 > iodepth=3Dint > Number of I/O units to keep in flight against the > file. Note that increasing iodepth beyond 1 will > not affect synchronous ioengines (except for small > degress when verify_async is in use). Even async > engines my impose OS restrictions causing the > desired depth not to be achieved. This may happen > on Linux when using libaio and not setting > direct=3D1, since buffered IO is not async on that > OS. Keep an eye on the IO depth distribution in > the fio output to verify that the achieved depth > is as expected. Default: 1. >=20 > Okay, yes, it does. I start getting a hang on it. Its a bit puzzling to > have two concepts of synchronous I/O around: >=20 > 1) synchronous system call interfaces aka fio I/O engine >=20 > 2) synchronous I/O requests aka O_SYNC But isn=EF=BF=BDt this a case for iodepth=3D1 if buffered I/O on Linux is=20 synchronous? I bet most regular applications except some databases use=20 buffered I/O. --=20 Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7