Hi, Mladen Nikitovic wrote:
Hi,I've been informed that there is a "power-aware" version of the original idle-thread in OpenSolaris. My understanding is that this version should execute the halt-instruction, which in turn disables the clock-tree of the processor. In the original version, the idle-thread continues checking different queues etc. As the power-aware idle-thread is not used by default, I'm wondering how I can go about replacing the original idle-thread? Is there a smooth approach? Would be happy for any pointers...At this point I'm not exactly aware of where the code for the power-aware idle thread is located in the source-tree.
The common idle loop is idle() in uts/common/disp/disp.c. Have a look
at its source and you'll see it calls the function pointed to by
idle_cpu when it can find no work to do. The uniprocessor loop
is easier to follows:
while (ncpus == 1) {
if (cp->cpu_disp->disp_nrunnable == 0) {
(*idle_cpu)();
continue;
}
idle_exit();
swtch();
idle_enter(); /* returned from swtch */
}
Different architectures can assign custom idle function to
idle_cpu. The default is generic_idle_cpu (see definition
of idle_cpu pointer in disp.c). For i86pc it can be
set to cpu_idle or to cpu_idle_mwait.
cpu_idle calls mach_cpu_idle which for i86pc calls the
halt instruction you refer to.
cpu_idle_mwait is a variant on systems that support monitoring
a line of memory for their wakeup condition (halt support
above uses an interrupt).
These are basic power awareness aspects - no frequency scaling, voltage
change etc. There is now support for Intel Speedstep. I've lost
track of the story for AMD - I know we decided it can't be
done on multiprocessor systems before family 0x10, but I vaguely
recall an intention to try it for family 0xf for single-socket
systems.
Gavin
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