Messages in this thread | | | Date | Mon, 25 May 2009 08:56:46 +0800 | From | Shaohua Li <> | Subject | Re: [patch 2/2] x86: put offline CPUs into deepest mwait cstate_subcstate |
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On Sat, May 23, 2009 at 07:19:42AM +0800, Pallipadi, Venkatesh wrote: > Offline CPUs can save power by going into deepest cstate, subcstate > instead of hlt loop. > > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> > --- > arch/x86/kernel/acpi/cstate.c | 51 +++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 51 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c > index bbbe4bb..5b0988a 100644 > --- a/arch/x86/kernel/acpi/cstate.c > +++ b/arch/x86/kernel/acpi/cstate.c > @@ -150,6 +150,54 @@ void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx) > } > EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter); > > +static unsigned long mwait_play_dead_eax; > + > +static void mwait_play_dead(void) > +{ > + if (boot_cpu_data.x86 >= 4) > + wbinvd(); > + > + while (1) { > + __monitor((void *)¤t_thread_info()->flags, 0, 0); > + smp_mb(); > + __mwait(mwait_play_dead_eax, 0); > + } > +} CPU is dead, can current_thread_info() still be used? Maybe just monitor a never changed address.
Looks the patch will always take the highest native C-state, is this safe, considering BIOS usually limit C-state?
Thanks, Shaohua
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