Hi,
2007/5/23, Bill Holler <Bill.Holler at sun.com>:
> Thomas De Schampheleire wrote:
> > Hi,
> >
> > In uts/sun4u/os/mach_startup.c, there is a function
> > mach_cpu_halt_idle() which is called from startup_end() in
> > uts/sun4u/os/startup.c
> >
> > This function has the following contents:
> >
> > 385 void
> > 386 mach_cpu_halt_idle()
> > 387 {
> > 388 if (enable_halt_idle_cpus) {
> > 389 if (&cpu_halt_cpu) {
> > 390 idle_cpu = cpu_halt;
> > 391 disp_enq_thread = cpu_wakeup;
> > 392 }
> > 393 }
> > 394 }
> >
> > The cpu_halt_cpu() function is only defined for some platforms, in
> > sun4u the only one I find is "olympus".
> >
> > In my research project we are using a full system simulator in which
> > OpenSolaris runs. I would like to make OpenSolaris believe that
> > halting is possible by providing my own cpu_halt_cpu() function.
> >
> > If I provide such a function in a kernel module, can I then re-call
> > mach_cpu_halt_idle() in order to overwrite the idle_cpu() and
> > disp_enq_thread() pointers? Or will this result in panic or incorrect
> > behavior?
> >
> No. mach_cpu_halt_idle() should only be called in system startup
> before scheduling starts. mach_cpu_halt_idle() was not intended to
> change the idle_cpu and disp_enq_thread function pointers on the fly.
>
> *You could modify cpu_halt() and cpu_wakeup() and your new
> functions to handle changing on a live system.
>
> > If this is not possible from a module, I would like to statically add
> > this cpu_halt_cpu() to the correct file in uts/sun4u/cpu/ so it is
> > seen at startup. I don't know which one this would be however. I am
> > simulating a serengeti machine, but there are no serengeti-specific
> > files in this directory. Shall I then simply put the code in the
> > us3_common files?
> Later Serengeti systems have cheetah processors. Either
> uts/sun4u/cpu/us3_common* or uts/sun4u/cpu/us3_cheetah* files
> should work.
>
>
> >
> > Just to be sure: this halt_cpu mechanism will overwrite the idle loop
> > so as to halt upon idling, and wakeup when some task has to run,
> > right? This halting can enable energy savings.
>
> Yes. I assume your new implementation will use poke_cpu() to
> wake up the idle cpus with an Inter Processor Interrupt?
I'm not exactly sure why you assume this and what you mean.
The implementation of cpu_halt_cpu() in olympus is:
1923 ENTRY_NP(cpu_halt_cpu)
1924 .word 0x81b01040
1925 retl
1926 nop
1927 SET_SIZE(cpu_halt_cpu)
I'm not exactly sure what the .word instruction does (manual says:
Generates (a sequence of) initialized words in the current segment.),
but I suppose it is used here to set some value.
What I planned was to remove that, and inside cpu_halt_cpu() use a so
called 'magic instruction' that signals a certain condition to the
simulator, and then simply return.
For the wakeup: I assumed that this would work like it is now, there
doesn't seem to be a hardware dependent function for that, right?
Thomas
>
> Regards,
> Bill Holler
>
> > Thanks, Thomas
> > _______________________________________________
> > tesla-dev mailing list
> > tesla-dev at opensolaris.org
> > http://opensolaris.org/mailman/listinfo/tesla-dev
>
>
