Hi!
> just an idle question out of the blue, over the last few releases, i've
> noticed kapmd is taking anywhere between 10 and 40% of the cpu. it
> isn't having a huge impact most of the time but does contribute.
It happens here, too.
I'm just taking a look. The code is perverted.
If system is idle (that is measured once a second *), it starts
spinning within the loop telling bios that we are idle. That "idle
call" in a loop is maybe done with disabled interrupts (damaging
killing interrupt response?)
What is more funny is that in case of cpu being idle, apm_do_idle() is
probably going to be called only half of a time. See:
schedule_timeout(HZ)
apm_do_idle()
while (1)
if (jiffies-start > HZ)
break
and repeat. That gives calls being done only half of a time. Patch
appended.
* -- what happens if there's _another_ program that wakes up once a
second? I think that with 0.01 probability apm_do_idle() will be never
called on such system. I think that this is ugly and that it can hurt
in real life.
--- clean/arch/i386/kernel/apm.c Sat Sep 11 20:55:53 1999
+++ linux/arch/i386/kernel/apm.c Mon Oct 11 21:56:50 1999
@@ -1073,8 +1078,10 @@
unsigned long start = jiffies;
do {
apm_do_idle();
- if (jiffies - start > APM_CHECK_TIMEOUT)
- break;
+ if (jiffies - start > APM_CHECK_TIMEOUT) {
+ apm_event_handler();
+ start = jiffies;
+ }
} while (system_idle());
apm_do_busy();
apm_event_handler();
--
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