I was experimenting with the attached program (taken from an IBM 
Developerworks article) to find the context switch times on AMD64 machine.

With a 64bit binary I get average 5 to 8 usec/cswitch, whereas the same 
program compiled as 32bit consistently gives >= 10 usec/cswitch - sometimes 
even 13 usec/cswitch.

Are there more context switching overheads when running 32bit programs on a 
64bit kernel?

Kernel version is 2.6.11-gentoo x86_64.
64bit compile  - g++ -O2 -pthread csfast5.cpp -ocsfast64
32bit compile  - g++ -m32 -O2 -pthread csfast5.cpp -ocsfast32
Run - ./csfast{32/64} -t 40 -c4 10

Parag