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Old 05-09-11, 02:29 PM   #1
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Join Date: May 2011
Posts: 2
Default Forcedeth on MCP67- jumbo-frames and 50% packet loss on 2.6.38?


i've got a MCP67-type ethernet connector which worked fine so far. I just recently upgraded to gigabit ethernet which led me to try to increase the my mtu to increase throughput. I found that on 2.6.35 this didn't work with a "SIOCSIFMTU: Invalid argument" with all values >1500. So i browsed the commits to forcedeth.c in the mainline kernel a bit and something led me to believe that it'd work in kernel after 2.6.37 - so i've tried a few recent kerneles, in fact almost all from 2.6.37 upwards. All of them exhibited a a problem with the forcedeth driver (or something else) - they lost over 50% of the packets, regardless of linkstate (i've tried all link speeds/duplex configs via ethtool) and remote station or cable (i've tried a few combinations). In all cases over 50% paket loss - that can't be right...

so my question is - is that a known problem? If so, is there a fix yet? And more importantly - can the MCP67 do jumbo frames at all? (i'm not that sure anymore - but why would anyone build a gigabit ethernet controller without jumbo frame support ... doesn't make that much sense, wasting so much throughput-potential...).

Thanks in Advance, and Kind Regards
- Dario Ernst
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