Subject: HW checksumming -- take 3
To: None <>
From: Jason R Thorpe <>
List: tech-net
Date: 05/19/2001 14:27:29
swinger:thorpej 6$ vmstat -e
event                               total     rate type
gsip0 txintr                        91806       84 intr
gsip0 rxintr                        96482       89 intr
gsip0 rxipsum                       96430       89 misc
gsip0 rxtcpsum                      96430       89 misc
gsip0 txipsum                       91685       84 misc
gsip0 txtcpsum                      90328       83 misc
swinger:thorpej 7$ 

Hardware out-bound TCP checksums are now working.  I'll do UDP soon, and
then work on fixing a bug in the x86-specific in4_cksum() so that software
checksums are fast again :-)

BTW, these changes make the outbound path use in4_cksum() now, rather
than in_cksum().  This means that ports that have not yet implemented
an optimized in4_cksum() should do so ASAP.

There will now be some further optimization to do for software checksums,
but it will be pretty low-hanging fruit.

        -- Jason R. Thorpe <>