Re: Accelerating user mode linux

[Richard Zidlicky]

On Thu, Aug 01, 2002 at 11:40:28PM -0500, Jeff Dike wrote:
> 
> Your objection to returning through sigreturn was performance.  Is performance
> a veto of adding an mm switch to sigreturn, or it is possible to make it
> acceptible?

I have once ported Basilisk to work native on linux-m68k. It works
*slow* so I looked what the problem is - the signal delivery in
Linux is exorbitantly slow. Eg an SIGILL delivery costs ~ 1650 cycles 
on a 68060, compared to that sigreturn and getpid are 200-250 and 
sched_yield with context switch around 400.

So sigreturn is not the place I would be looking for the biggest
speedups.

Richard