Hi,
I just compiled 2.4.16 for my notebook with "Make CPU Idle calls when idle"
enabled. Now kapm-idled uses up to 50% cpu when the system is otherwise
idle. Is that correct? It is quite disturbing to have 50% System load when
the system is supposed to be idle.
Greetings
Gert
On Tue, 2001-12-04 at 15:18, Gert Menke wrote:
> I just compiled 2.4.16 for my notebook with "Make CPU Idle calls when idle"
> enabled. Now kapm-idled uses up to 50% cpu when the system is otherwise
> idle. Is that correct? It is quite disturbing to have 50% System load when
> the system is supposed to be idle.
Yes, this is the correct behavior. I agree it is annoying.
Robert Love
On Tue, 4 Dec 2001, Gert Menke wrote:
> I just compiled 2.4.16 for my notebook with "Make CPU Idle calls when idle"
> enabled. Now kapm-idled uses up to 50% cpu when the system is otherwise
> idle. Is that correct? It is quite disturbing to have 50% System load when
> the system is supposed to be idle.
http://www.tux.org/lkml/#s14-1
Dave.
--
| Dave Jones. http://www.codemonkey.org.uk
| SuSE Labs
Hi,
On Tue, Dec 04, 2001 at 09:45:44PM +0100, Dave Jones wrote:
> http://www.tux.org/lkml/#s14-1
Sorry, I should have read the FAQ first.
But it is still annoying that kapm-idled claims to use that much system
ressources when it isn't. When my system is idle it should say ~100% idle,
not ~50% system. Right?
Is there an easy way to fix this? Or a good reason not to?
Greetings
Gert
Hi,
the problem is that kapm-idled and the idle task are both trying to handle the
system idle time. I did send a patch correcting this weird behaviour for
revision to Alan Cox a few days ago but until now there's no reaction from him.
Oh, and there's more problems with kapm-idled. Think of a task like kmix that
is ready to run every fraction of HZ to do some bookkeeping. Now look at the
kapm-idled code. If both run in sync, e.g. they are ready to run during the
same time slice kapm-idled will never do bios idle calls as there's always at
least one task ready to run and this is then accounted as a 'heavily loaded
system'.
If you want to have a look at the patch please let me know though it may take a
few days. I have to recover a system suffering from severe bit errors due to
a memory module having gone south very slowly and quiet.
On 04-Dec-2001 Gert Menke wrote:
> Hi,
>
> On Tue, Dec 04, 2001 at 09:45:44PM +0100, Dave Jones wrote:
>> http://www.tux.org/lkml/#s14-1
> Sorry, I should have read the FAQ first.
>
> But it is still annoying that kapm-idled claims to use that much system
> ressources when it isn't. When my system is idle it should say ~100% idle,
> not ~50% system. Right?
> Is there an easy way to fix this? Or a good reason not to?
>
> Greetings
> Gert
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
Andreas Steinmetz
D.O.M. Datenverarbeitung GmbH
> system idle time. I did send a patch correcting this weird behaviour for
> revision to Alan Cox a few days ago but until now there's no reaction from him.
It looks quite sensible to me (I thought i had replied)
> If you want to have a look at the patch please let me know though it may take a
> few days. I have to recover a system suffering from severe bit errors due to
> a memory module having gone south very slowly and quiet.
Your patch attached below
--
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Date: Sat, 01 Dec 2001 19:11:27 +0100 (CET)
Organization: D.O.M. Datenverarbeitung GmbH
From: Andreas Steinmetz <[email protected]>
To: Alan Cox <[email protected]>
Subject: [PATCH] apm fix for broken CONFIG_APM_CPU_IDLE
Status: RO
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Hi,
I did some analysis of APM for CONFIG_APM_CPU_IDLE as it just doesn't work as
expected. There are major deficiencies:
1. kapm-idled can't reliably handle APM idle calls as it may (and quite often
does) run in sync with other processes that are ready to run e.g. on a
select timeout but do only negigable processing until sleeping again
(already reported).
2. kapm-idled does account as system load while doing idle calls. Furthermore
the idle task cannot run while kapm-idled is running which can cause
excess battery draining on laptops where the BIOS only slows the clock on
APM idle calls. On the other hand on systems where the APM bios stops the
clock may do additional power saving the additional power saving may not
occur while kapm-idled is suspended and only system idling does occur.
3. The system may be slowed down unnecessarily by excess APM BIOS idle calls as
kapm-idled doesn't take the average system load into account.
As far as I can see CONFIG_APM_CPU_IDLE should behave like this:
1. APM BIOS idle calls should be done when the system is nearly idle, otherwise
standard idle handling should be done.
The decision whether to do standard idle handling or to do APM BIOS calls
needs to be done on a system load estimate during a certain time period.
2. When the APM BIOS stops the clock no standard idle handling is required.
Note that in case of a broken APM BIOS signalling stopping of the CPU but
not doing so the current handling is broken and configuring without
CONFIG_APM_CPU_IDLE is anyway required.
3. When the APM BIOS just slows the clock standard idle handling is required in
addition to the BIOS idle calls.
The attached patch implements the behaviour as described above:
1. APM BIOS idle call handling is completely removed from kapm-idled and placed
in the reworked and 'reanimated' apm_cpu_idle function.
2. apm_cpu_idle is an 'in between' APM shim that calls the previously installed
system idle function as required.
3. The decision wether to use APM idle calls or doing standard idle calls is
based on the percentage of idle time during the last third of a second.
More than 95% of idle time during this period causes APM idle calls to be
used instead of standard idle handling.
4. I don't know if the patch is SMP safe as I do only have UP systems. It does
however, run well on my laptop which did have problems with APM idle
handling since my switch from 2.2 to 2.4.
I would ask you to review this patch as it does bring CONFIG_APM_CPU_IDLE back
to a working state which should really help linux laptop users.
If you can agree on the patch I would like to post it to lkml for kernel
inclusion.
Andreas Steinmetz
D.O.M. Datenverarbeitung GmbH
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diff -rNu linux/arch/i386/kernel/apm.c linux-custom/arch/i386/kernel/apm.c
--- linux/arch/i386/kernel/apm.c Sat Dec 1 18:12:50 2001
+++ linux-custom/arch/i386/kernel/apm.c Sat Dec 1 18:12:40 2001
@@ -735,63 +735,71 @@
}
}
-#if 0
-extern int hlt_counter;
-
/*
- * If no process has been interested in this
- * CPU for some time, we want to wake up the
- * power management thread - we probably want
+ * If no process has really been interested in
+ * CPU for some time, we want to call BIOS
+ * power management - we probably want
* to conserve power.
*/
#define HARD_IDLE_TIMEOUT (HZ/3)
+#define IDLE_CALC_LIMIT (HZ*100)
+#define BIOS_IDLE_TRIGGER 95
-/* This should wake up kapmd and ask it to slow the CPU */
-#define powermanagement_idle() do { } while (0)
+static void (*sys_idle)(void);
+static unsigned int last_jiffies = 0;
+static unsigned int last_stime = 0;
+static int use_apm_idle = 0;
/**
* apm_cpu_idle - cpu idling for APM capable Linux
*
* This is the idling function the kernel executes when APM is available. It
- * tries to save processor time directly by using hlt instructions. A
- * separate apm thread tries to do the BIOS power management.
- *
- * N.B. This is curently not used for kernels 2.4.x.
+ * tries to do BIOS powermanagement based on the average system idle time.
+ * Furthermore it calls the system default idle routine.
*/
static void apm_cpu_idle(void)
{
- unsigned int start_idle;
-
- start_idle = jiffies;
- while (1) {
- if (!current->need_resched) {
- if (jiffies - start_idle < HARD_IDLE_TIMEOUT) {
- if (!current_cpu_data.hlt_works_ok)
- continue;
- if (hlt_counter)
- continue;
- __cli();
- if (!current->need_resched)
- safe_halt();
- else
- __sti();
- continue;
- }
+ int apm_is_idle = 0;
+ unsigned int t1 = jiffies - last_jiffies;
+ unsigned int t2;
+
+recalc: if(t1 > IDLE_CALC_LIMIT)
+ goto reset;
+
+ if(t1 > HARD_IDLE_TIMEOUT) {
+ t2 = current->times.tms_stime - last_stime;
+ t2 *= 100;
+ t2 /= t1;
+ if (t2 > BIOS_IDLE_TRIGGER)
+ use_apm_idle = 1;
+ else
+reset: use_apm_idle = 0;
+ last_jiffies = jiffies;
+ last_stime = current->times.tms_stime;
+ }
- /*
- * Ok, do some power management - we've been idle for too long
- */
- powermanagement_idle();
+ while (!current->need_resched) {
+ if(use_apm_idle)
+ switch (apm_do_idle()) {
+ case 0: apm_is_idle = 1;
+ continue;
+ case 1: apm_is_idle = 1;
+ break;
}
- schedule();
- check_pgt_cache();
- start_idle = jiffies;
+ if (sys_idle)
+ sys_idle();
+
+ t1 = jiffies - last_jiffies;
+ if (t1 > HARD_IDLE_TIMEOUT)
+ goto recalc;
}
+
+ if (apm_is_idle)
+ apm_do_busy();
}
#endif
-#endif
#ifdef CONFIG_SMP
static int apm_magic(void * unused)
@@ -1346,17 +1354,12 @@
static void apm_mainloop(void)
{
- int timeout = HZ;
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(&apm_waitqueue, &wait);
set_current_state(TASK_INTERRUPTIBLE);
for (;;) {
- /* Nothing to do, just sleep for the timeout */
- timeout = 2 * timeout;
- if (timeout > APM_CHECK_TIMEOUT)
- timeout = APM_CHECK_TIMEOUT;
- schedule_timeout(timeout);
+ schedule_timeout(APM_CHECK_TIMEOUT);
if (exit_kapmd)
break;
@@ -1366,34 +1369,6 @@
*/
set_current_state(TASK_INTERRUPTIBLE);
apm_event_handler();
-#ifdef CONFIG_APM_CPU_IDLE
- if (!system_idle())
- continue;
-
- /*
- * If we can idle...
- */
- if (apm_do_idle() != -1) {
- unsigned long start = jiffies;
- while ((!exit_kapmd) && system_idle()) {
- if (apm_do_idle()) {
- set_current_state(TASK_INTERRUPTIBLE);
- /* APM needs us to snooze .. either
- the BIOS call failed (-1) or it
- slowed the clock (1). We sleep
- until it talks to us again */
- schedule_timeout(1);
- }
- if ((jiffies - start) > APM_CHECK_TIMEOUT) {
- apm_event_handler();
- start = jiffies;
- }
- }
- apm_do_busy();
- apm_event_handler();
- timeout = 1;
- }
-#endif
}
remove_wait_queue(&apm_waitqueue, &wait);
}
@@ -1968,12 +1943,21 @@
misc_register(&apm_device);
+#ifdef CONFIG_APM_CPU_IDLE
+ sys_idle=pm_idle;
+ pm_idle=apm_cpu_idle;
+#endif
+
return 0;
}
static void __exit apm_exit(void)
{
int error;
+
+#ifdef CONFIG_APM_CPU_IDLE
+ pm_idle=sys_idle;
+#endif
if (((apm_info.bios.flags & APM_BIOS_DISENGAGED) == 0)
&& (apm_info.connection_version > 0x0100)) {
--_=XFMail.1.5.1.Linux:20011201191127:1153=_--
End of MIME message
Hi!
On Wed, Dec 05, 2001 at 09:07:20AM +0000, Alan Cox wrote:
> > system idle time. I did send a patch correcting this weird behaviour for
> > revision to Alan Cox a few days ago but until now there's no reaction from him.
> It looks quite sensible to me (I thought i had replied)
> [...]
> Your patch attached below
Okay, this seems to work well.
Thank you!
Any chance to see this included in 2.4. soon? That would be great.
Greetings
Gert