RE: [patch 3/6] prefetch bottom of kernel rbs stack at syscall exit path

Chen, Kenneth W
2006-02-07T21:27:32Z

David Mosberger-Tang wrote on Tuesday, February 07, 2006 1:19 PM
> > Chen, Kenneth wrote on Tuesday, January 31, 2006 11:27 AM
> > > David Mosberger-Tang wrote on Tuesday, January 31, 2006 9:45 AM
> > > > How much latency does this add for a minimal syscall when
> > > > everything is cached?
> > >
> > > I will get the measurement out shortly.
> >
> > Here are the numbers for break based getpid():
> >
> > Vanilla 2.6.15: 238 cycles
> > Vanilla + patches: 250 cycles
>
> Hmmh, 12 cycles lost. Can you see if you can do better? There really
> are apps out there that care about this case (not getpid per se, but
> minimal syscall entry/exit overhead when everything is cached).

I'm with you completely on this. I'm not happy with it either. So back
to the drawing board.

- Ken