On Thu, 19 Feb 2004, Marian Durkovic wrote:
Hi all,
the performance problem seems to disappear, when the hardware checksuming for TX direction is disabled (RX hw checksuming still on). Here are the results:
Hm... This, combined with Matt blaming the Tx checksum for corrupting packets seems to spell the end for 3Com 905 checksumming. I'll turn it off in a few days.
Thanks for the good detective work.
Putting the corrupted packets issue aside I have no problem with a 3c905c hitting 92 Mb/s on a old celeron 333 using a modified if_xl.c under fbsd 4.5:
blah# ttcp -r -s ttcp-r: buflen=8192, nbuf=2048, align=16384/0, port=5001 tcp ttcp-r: socket ttcp-r: accept from 192.168.63.20 ttcp-r: 33554432 bytes in 2.91 real seconds = 11262.49 KB/sec +++ ttcp-r: 10210 I/O calls, msec/call = 0.29, calls/sec = 3509.22 ttcp-r: 0.0user 0.5sys 0:02real 18% 15i+207d 196maxrss 0+2pf 10184+9csw
blah# ttcp -t -s -n4096 stink ttcp-t: buflen=8192, nbuf=4096, align=16384/0, port=5001 tcp -> stink ttcp-t: socket ttcp-t: connect ttcp-t: 33554432 bytes in 2.90 real seconds = 11309.62 KB/sec +++ ttcp-t: 4096 I/O calls, msec/call = 0.72, calls/sec = 1413.70 ttcp-t: 0.0user 0.6sys 0:02real 24% 19i+299d 246maxrss 0+2pf 10154+1csw
The modification was to reduce the NIC interrupt rate via a rudimentary hardware polling scheme based on the 3c905x countdown timer.
Can't find the notes I made on the performance improvement although it was reasonable (something like 5-10% if my memory is correct) for my
hardware.
Probably should have someone with more understanding of kernel drivers check whether it has any application outside my home office... :-)
David
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