My guess is that you are measuring latency.  By default, interrupt  
coalescing is on, and used to be set to very poor default values.  In  
drivers/net/gianfar.h, change the defaults to look like this:

#define DEFAULT_TX_COALESCE 1
#define DEFAULT_TXCOUNT 16
#define DEFAULT_TXTIME  4

#define DEFAULT_RX_COALESCE 1
#define DEFAULT_RXCOUNT 16
#define DEFAULT_RXTIME  4

The problem was that the timeout was quite long, so a small number of  
packets would have to wait a whole millisecond (or more!) to get  
processed.  While it wouldn't affect bandwidth tests, which send many  
packets, it would affect a simple test like ping.

If you don't feel like recompiling the kernel, you can use ethtool to  
change the timeout values.


On Feb 14, 2006, at 09:26, Laurent Lagrange wrote:

Hello,

I work on a cutom MPC8541 board with Linux 2.6.9.
The kernel activates the L1 cache (instructions and data)
and the L2 cache (entirely used as cache and not as sram).

I configure
1 FCC (FCC1),
2 TSECs with or without NAPI (no effect) but without stashing in L2  
sram.
All PHYs are automatically configured in 100MB full duplex.

	eth0: Gianfar Ethernet Controller Version 1.1, 00:10:cd:48:48:e0
	eth0: Running with NAPI disabled
	eth0: 64/64 RX/TX BD ring size
	eth1: Gianfar Ethernet Controller Version 1.1, 00:10:cd:48:48:e1
	eth1: Running with NAPI disabled
	eth1: 64/64 RX/TX BD ring size
	eth2: FCC ENET Version custom, 00:10:cd:48:48:e2

Then I launch 3 simple TCP servers, one on each ports.

quoted

From remote machines I runs 3 TCP clients.

The client sends messages of 1000 bytes,
The server receives and echoes the message
The client receives the echoed message, check the content
and sends a new message again.

The result is that the 2 TSECs are 2 times slower than the FCC.

If I run a "top" application on the board, I use less than 10% of  
the CPU
Each port consumes about 1/3 of the CPU.

Any idea on how to configure the gianfar driver ?

Thanks
Laurent


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