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Date: Thu, 26 Mar 2015 00:20:42 +0800
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From: Cheng Kevin <k5896246@gmail.com>
To: Bruce Richardson <bruce.richardson@intel.com>
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Subject: Re: [dpdk-dev] DPDK testpmd, Virtual Disk IO limitation
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Mr. Bruce Richardson

Yes, you are right. This really bother me.

Is there any way to get rid of system call? Maybe some DPDK threading API?
Maybe i should use a extra nic card for posting the data out through
internet, instead of writing on the disk - ex. fwrite.

Or you have some better advises??

Thanks
Kevin


2015-03-25 23:01 GMT+08:00 Bruce Richardson <bruce.richardson@intel.com>:

> 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
>