From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruce Richardson Subject: Re: DPDK testpmd, Virtual Disk IO limitation Date: Wed, 25 Mar 2015 15:01:57 +0000 Message-ID: <20150325150156.GA5620@bricha3-MOBL3> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev-VfR2kkLFssw@public.gmane.org To: Cheng Kevin Return-path: Content-Disposition: inline In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" On Wed, Mar 25, 2015 at 10:06:48PM +0800, Cheng Kevin wrote: > Hi all, > > I am a beginner of DPDK. Recently, i am interest in DPDK vHost app - > testpmd. > > And i have been tracing on testpmd.c and iofwd.c for a while. > > Also add some code inside iofwd.c for storing the payload of packets. > > Everything goes fine, and the performance is great as expected. > > But when i use fwrite to store the payload into a file, > > the performance decrease from 800mbps to 3mbps (input stream is 1 Gbps). > > Is is caused by the limitation of Virtual Disk IO? How can i solve it? > > I have tried to search the answer, some people say "pthread" might solve > the problem. > > Can someone give me some hint, i really appreciate for your help. > > > Best Regard, > > Kevin Cheng Two general issues you will hit writing to disk: 1) IO, including disk IO, is slow 2) System calls are slow. You are probably hitting both bottlenecks. /Bruce