Re: look strange tx rate on my board!!!!


From: Jouni Malinen (jkmaline_at_cc.hut.fi)
Date: 2002-08-24 16:20:27 UTC



On Thu, Aug 22, 2002 at 03:20:21PM +0900, 조대우 wrote:

> Main processor is the MPC 855T, and my board has a PCMCIA slot for WLAN PCMCIA Card.
> However, the tx rate of my board is something wrong.
>
> external ftp server ---(100M Ethernet)---> my board ---(wireless)---> ftp client(notebook)
> At this environment, download rate is 300Kbytes/sec
>
> ftp client(notebook) ---(wireless)---> my board ---(100M Ethernet)---> external ftp server
> At this environment, upload rate is 600Kbytes/sec

I would recommend first using a performance test that would not include any external components for more reliable results.. Something like UDP speed test with netperf in both directions between an AP and a STA associated to it (i.e., no routing/bridging).

Can you get some data from the host CPU load during the traffic load? What about interrupt handling? TX will generate more interrupts (two per packet) than RX (one per packet). If I remember correctly, TX path also uses bit more CPU cycles that RX, so if the host CPU is near its capacity limits, this might be causing some difference in RX/TX speeds.

How old is the Host AP driver version you are using? I have done some optimizations on command completion handling (e.g., removed busy waiting etc.) that might help on some host platforms. These are available in the CVS snapshot version, but not in the latest release version.

-- 
Jouni Malinen                                            PGP id EFC895FA


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