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

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Message-ID: <c2178680812092230t493b9212pdfb721cde15bf89a@mail.gmail.com>
Date:	Wed, 10 Dec 2008 14:30:10 +0800
From:	"Zhiwen Zheng" <zhiwen.zh@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: IP over Fibre Channel slower than GigaEthernet ?

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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