diff options
Diffstat (limited to 'sys/i386/i386/machdep.c')
-rw-r--r-- | sys/i386/i386/machdep.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c index 8b1b08b..a3c09f4 100644 --- a/sys/i386/i386/machdep.c +++ b/sys/i386/i386/machdep.c @@ -72,6 +72,7 @@ #include <sys/sysctl.h> #include <sys/vmmeter.h> #include <sys/bus.h> +#include <sys/eventhandler.h> #include <vm/vm.h> #include <vm/vm_param.h> @@ -1005,6 +1006,42 @@ cpu_halt(void) } /* + * Hook to idle the CPU when possible. This currently only works in + * the !SMP case, as there is no clean way to ensure that a CPU will be + * woken when there is work available for it. + */ +#ifndef SMP +static int cpu_idle_hlt = 1; +SYSCTL_INT(_machdep, OID_AUTO, cpu_idle_hlt, CTLFLAG_RW, &cpu_idle_hlt, 0, "Idle loop HLT enable"); + +/* + * Note that we have to be careful here to avoid a race between checking + * procrunnable() and actually halting. If we don't do this, we may waste + * the time between calling hlt and the next interrupt even though there + * is a runnable process. + */ +static void +cpu_idle(void *junk, int count) +{ + if (cpu_idle_hlt){ + disable_intr(); + if (procrunnable()) { + enable_intr(); + } else { + enable_intr(); + __asm__ ("hlt"); + } + } +} + +static void cpu_idle_register(void *junk) +{ + EVENTHANDLER_FAST_REGISTER(idle_event, cpu_idle, NULL, IDLE_PRI_LAST); +} +SYSINIT(cpu_idle_register, SI_SUB_SCHED_IDLE, SI_ORDER_SECOND, cpu_idle_register, NULL) +#endif /* !SMP */ + +/* * Clear registers on exec */ void |