From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [RFC] relaxed barrier semantics Date: Fri, 06 Aug 2010 22:38:46 +0400 Message-ID: <4C5C56B6.9020309@vlnb.net> References: <4C4FECFE.9040509@kernel.org> <20100728085048.GA8884@lst.de> <4C4FF136.5000205@kernel.org> <20100728090025.GA9252@lst.de> <4C4FF592.9090800@kernel.org> <20100728092859.GA11096@lst.de> <20100802173930.GP16630@think> <4C5AB89C.5080700@vlnb.net> <20100805133225.GF29846@think> <4C5B1583.6070706@vlnb.net> <20100805195048.GA19030@lst.de> <4C5B19A0.9070200@vlnb.net> <4C5C22B8.9040109@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Christoph Hellwig , Chris Mason , Vivek Goyal , Jan Kara , jaxboe@fusionio.com, James.Bottomley@suse.de, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, tytso@mit.edu, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp To: Hannes Reinecke , Tejun Heo Return-path: Received: from moutng.kundenserver.de ([212.227.17.8]:49646 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935598Ab0HFSiz (ORCPT ); Fri, 6 Aug 2010 14:38:55 -0400 In-Reply-To: <4C5C22B8.9040109@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hannes Reinecke, on 08/06/2010 06:56 PM wrote: > But I can do bonnie runs in no time. > I have done some preliminary benchmarks by just enable ordered > queueing in sd.c and no other changes. > Bonnie says: > > Writing intelligently: 115208 vs. 82739 > Reading intelligently: 134133 vs. 129395 > > putc() performance suffers, though: > I get 52M vs 90M writing and 50M vs. 65M reading. > No idea why; shouldn't be that harmful here. > > But in any case there is some speed improvement > to be had from using ordered tags. > > Oh, and that was against an EVA 6400. Here are my numbers. They are taken using: fio --bs=X --ioengine=aio --buffered=0 --size=128M --rw=read --thread --numjobs=1 --loops=100 --group_reporting --gtod_reduce=1 --name=AAA --filename=/dev/sdc --iodepth=Y /dev/sdc is 1GbE iSCSI device with on the other side iSCSI-SCST with a single 15K RPM Wide SCSI HDD. All values are in MB/s. The system (initiator) is pretty old 1.7GHz Xeon. Y | 1 2 4 8 32 ---------------------------------------------------------------------- X | 4K | 16 25 32 34 34 (initiator CPU overloaded) 16K | 25 57 72 85 85 (initiator CPU overloaded) 32K | 44 72 97 106 106 (initiator CPU overloaded) 64K | 65 95 114 115 115 (max of 1GbE) 128K | 80 112 115 115 115 (max of 1GbE) Are there still any people thinking that tagged queuing doesn't have any meaningful use? Or 350% performance increase doesn't matter? (If the system was more powerful, the difference would be even bigger.) As you can see on external storage even with 128K commands the queue should have at least 2 entries queued to go with full performance. Vlad