I just spent a while with Windows booted on the same hardware. With no trouble at all I am able to achieve 19Mb/sec of useful file copy throughput. With 11g 27Mb is max possible including all of the overhead, 19Mb useful copies is probably as good as it gets. In three hours of copying and measuring I never dropped a session.
Doing these tests has eliminated a lot potential problems. It shows that my router is working. It also shows that the the dropped packets are not the result of environmental noise. It also shows that the zd1211 hardware has no problem exchanging packets with my router at 54Mb with short preambles. All of this points to something wrong in the Linux device driver that is either corrupting packets or losing them. So next step is to start looking at the driver code and see if I can spot some sort of problem. This is a hard problem because a lot of the packets are making it through ok, only a few are being lost. After comparing the kismet traces of Windows to the Linux ones, it looks to me like my Nokia770 isn't fast enough to record everything and is dropping some of the packets. I've ordered some PCI based 11g hardware that should be fast enough to see everything. So bottom line, there is definitely a large difference between the Linux and Windows drivers at 54Mb, but so far I have no clue as to what is causing it. >From reading the mail about performance, what is considered a wlan jumbo frame? The longest frame I captured was 1468 bytes long. That is probably controlled by the MTU size of the TCP stack. Allocating memory instead of using a circular buffer may be the source of dropped packets. At 54Mb ack packets can arrive one every 2us which works out to over 500K interrupts per second. I'm not sure that an x86 desktop can respond to that level of interrupt load. Wire based hardware I have worked with used DMA and interrupt throttling to reduce the load. I'm not familiar with how USB deals with these problems so I need to read some more. -- Jon Smirl [EMAIL PROTECTED] ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Zd1211-devs mailing list - http://zd1211.ath.cx/ Unsubscribe: https://lists.sourceforge.net/lists/listinfo/zd1211-devs
