From: Anton Blanchard <anton@samba.org>
Now that we understand (and have fixed) the problem with using low power mode
in the idle loop, lets enable it. It should save a fair amount of power.
(The problem was that our exceptions were inheriting the low power mode and so
were executing at a fraction of the normal cpu issue rate. We fixed it by
always bumping our priority to medium at the start of every exception).
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/arch/ppc64/kernel/idle.c | 22 +++++++++++++---------
1 files changed, 13 insertions(+), 9 deletions(-)
diff -puN arch/ppc64/kernel/idle.c~ppc64-enable-power5-low-power-mode-in-idle-loop arch/ppc64/kernel/idle.c
--- 25/arch/ppc64/kernel/idle.c~ppc64-enable-power5-low-power-mode-in-idle-loop 2004-09-11 16:30:01.556195760 -0700
+++ 25-akpm/arch/ppc64/kernel/idle.c 2004-09-11 16:30:01.560195152 -0700
@@ -142,7 +142,12 @@ int default_idle(void)
while (!need_resched() && !cpu_is_offline(cpu)) {
barrier();
+ /*
+ * Go into low thread priority and possibly
+ * low power mode.
+ */
HMT_low();
+ HMT_very_low();
}
HMT_medium();
@@ -184,18 +189,18 @@ int dedicated_idle(void)
start_snooze = __get_tb() +
*smt_snooze_delay * tb_ticks_per_usec;
while (!need_resched() && !cpu_is_offline(cpu)) {
- /* need_resched could be 1 or 0 at this
- * point. If it is 0, set it to 0, so
- * an IPI/Prod is sent. If it is 1, keep
- * it that way & schedule work.
+ /*
+ * Go into low thread priority and possibly
+ * low power mode.
*/
+ HMT_low();
+ HMT_very_low();
+
if (*smt_snooze_delay == 0 ||
- __get_tb() < start_snooze) {
- HMT_low(); /* Low thread priority */
+ __get_tb() < start_snooze)
continue;
- }
- HMT_very_low(); /* Low power mode */
+ HMT_medium();
if (!(ppaca->lppaca.xIdle)) {
/* Indicate we are no longer polling for
@@ -210,7 +215,6 @@ int dedicated_idle(void)
break;
}
- /* DRENG: Go HMT_medium here ? */
local_irq_disable();
/* SMT dynamic mode. Cede will result
_