[User-mode-linux-devel] Performance enhancement idea...

[Chris L. <sa...@sk...>]

Hello all...

Currently, syscall entry requires the tracing thread to wake up, munge the
registers around, and do other stuff before the syscall'ing thread
continues in the kernel...  I have two ideas to improve syscall
performance:

1. Instead of changing EAX to make the syscall do a getpid, why not just
add 2 to the EIP to skip over the int 80?
2. Additionally, why not change that int 80 to be "ud2" or some other
opcode that will cause a SIGILL?  When receiving a sigill, just check for
the magic opcode and if it is set, do the syscall... this would have the
advantage that the ptrace/c-switch overhead would be reduced...

Does anyone see any problems with these suggestions?  I may be interested
in implementing them if not...

-Chris