linux-kernel - Re: IP over Fibre Channel slower than GigaEthernet ?

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Message-ID: <c2178680812101724o40df531aw2390e08e2938f4bb@mail.gmail.com>
Date:	Thu, 11 Dec 2008 09:24:37 +0800
From:	"Zhiwen Zheng" <zhiwen.zh@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: IP over Fibre Channel slower than GigaEthernet ?

Could someone point me to resources about doing zero copy in kernel,
such as RDMA over IP, RDMA over FC , please?

2008/12/10 Zhiwen Zheng <zhiwen.zh@...il.com>:
> Hi,
>
> To compare tcp transport speed of IP over FC to that of GigaEthernet,
> I have two machines connected directly with FC or GigaEther, and run
> ttcp to get the result.
>
> configuration of the machines:
> kernel version : 2.6.10
> platform : xscale iop80331 500MHz
> memory : 512MB DDR2
> FC controller : LSI FC949x (using driver mptlan.c)
> GigaEthernet controller : Intel 82546EB
>
>
> In the Ethernet case,  the transport speed is about 90MB/s,
> and cpu usage is about 90%.
>
> In the FC case, the transport speed is about 60MB/s,
> and cpu usage is also about 90%.
>
>  Could someone tell me why FC is slower than GigaEthernet?
> And is it possible to reduce the cpu usage through DMA or something else ?
>
> Thanks.
>
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