Rescheduling interrupts

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* Rescheduling interrupts
@ 2008-01-21 23:19 S.Çağlar Onur
  2008-01-22 10:57 ` Ingo Molnar
  0 siblings, 1 reply; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-21 23:19 UTC (permalink / raw)
  To: LKML; +Cc: Ingo Molnar, Arjan van de Ven

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Hi;

With Linus's latest git, powertop reports following while system nearly %100 
idle;

PowerTOP version 1.9       (C) 2007 Intel Corporation

Cn                Avg residency       P-states (frequencies)
C0 (cpu running)        ( 6,3%)         1,84 Ghz     0,4%
C1                0,0ms ( 0,0%)         1333 Mhz     0,0%
C2                0,1ms ( 0,5%)         1000 Mhz    99,6%
C3                3,7ms (93,2%)


Wakeups-from-idle per second : 306,8    interval: 10,0s
Power usage (5 minute ACPI estimate) :  23,1 W (0,5 hours left)

Top causes for wakeups:
  59,9% (238,4)      <kernel IPI> : Rescheduling interrupts
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  14,7% ( 58,6)         amarokapp : schedule_timeout (process_timeout)
   5,5% ( 21,9)              java : futex_wait (hrtimer_wakeup)
   5,0% ( 19,8)       <interrupt> : iwl3945
   2,5% ( 10,0)              java : schedule_timeout (process_timeout)
   2,5% ( 10,0)     <kernel core> : ehci_work (ehci_watchdog)
   2,5% ( 10,0)       <interrupt> : extra timer interrupt
   1,6% (  6,4)             artsd : schedule_timeout (process_timeout)
   1,0% (  4,0)   <kernel module> : usb_hcd_poll_rh_status (rh_timer_func)
   0,5% (  2,0)       <interrupt> : ohci1394, uhci_hcd:usb4, nvidia
   0,5% (  2,0)     <kernel core> : clocksource_check_watchdog 
(clocksource_watchdog)
   0,5% (  2,0)              kwin : schedule_timeout (process_timeout)
   0,5% (  1,9)    wpa_supplicant : schedule_timeout (process_timeout)
   0,3% (  1,2)          kdesktop : schedule_timeout (process_timeout)
   0,3% (  1,0)          kwrapper : do_nanosleep (hrtimer_wakeup)
   0,3% (  1,0)           klipper : schedule_timeout (process_timeout)
   0,3% (  1,0)             artsd : do_setitimer (it_real_fn)
   0,3% (  1,0)         gpg-agent : schedule_timeout (process_timeout)
   0,3% (  1,0)                 X : nv_start_rc_timer (nv_kern_rc_timer)
   0,3% (  1,0)            kicker : schedule_timeout (process_timeout)
   0,1% (  0,5)           iwl3945 : ieee80211_authenticate 
(ieee80211_sta_timer)
   0,1% (  0,5)     <kernel core> : neigh_table_init_no_netlink 
(neigh_periodic_timer)

This "<kernel IPI> : Rescheduling interrupts" causes at least 200 wakeups 
(sometimes i see ~400 wakeups) for me and a quick google search yields [1], 
but i didn't see this reported to LKML, so here it is :).

If anything else is needed please yell...

[1] http://www.mail-archive.com/power@bughost.org/msg01009.html
-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

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^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-21 23:19 Rescheduling interrupts S.Çağlar Onur
@ 2008-01-22 10:57 ` Ingo Molnar
  2008-01-22 12:55   ` S.Çağlar Onur
  0 siblings, 1 reply; 15+ messages in thread
From: Ingo Molnar @ 2008-01-22 10:57 UTC (permalink / raw)
  To: S.Çağlar Onur; +Cc: LKML, Arjan van de Ven

* S.Çağlar Onur <caglar@pardus.org.tr> wrote:

> Top causes for wakeups:
>   59,9% (238,4)      <kernel IPI> : Rescheduling interrupts
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>   14,7% ( 58,6)         amarokapp : schedule_timeout (process_timeout)

hm, would be nice to figure out what causes these IPIs. Could you stick 
something like this into arch/x86/kernel/smp_32.c's 
smp_send_reschedule() function [this is the function that generates the 
IPI]:

static void native_smp_send_reschedule(int cpu)
{
        WARN_ON(cpu_is_offline(cpu));
        send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR);
	if (panic_timeout > 0) {
		panic_timeout--;
		printk("IPI from task %s:%d on CPU#%d:\n", 
			current->comm, current->pid, cpu);
		dump_stack();
	}
}

NOTE: if you run an SMP kernel then first remove these two lines from 
kernel/printk.c:

        if (!oops_in_progress && waitqueue_active(&log_wait))
                wake_up_interruptible(&log_wait);

otherwise you'll get lockups. (the IPI is sent while holding the 
runqueue lock, so the printks will lock up)

then wait for the bad condition to occur on your system and generate a 
stream of ~10 backtraces, via:

	echo 10 > /proc/sys/kernel/panic

you should be getting 10 immediate backtraces - please send them to us. 
The backtraces should show the place that generates the wakeups. [turn 
on CONFIG_FRAME_POINTERS=y to get high quality backtraces.]

If you do _not_ get 10 immediate backtraces, then something in the 
system is generating such IPIs outside of the scheduler's control. That 
would suggest some other sort of borkage.

	Ingo

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 10:57 ` Ingo Molnar
@ 2008-01-22 12:55   ` S.Çağlar Onur
  2008-01-22 15:23     ` Ingo Molnar
  0 siblings, 1 reply; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-22 12:55 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: LKML, Arjan van de Ven

Hi;

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı: 
> * S.Çağlar Onur <caglar@pardus.org.tr> wrote:
> 
> > Top causes for wakeups:
> >   59,9% (238,4)      <kernel IPI> : Rescheduling interrupts
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >   14,7% ( 58,6)         amarokapp : schedule_timeout (process_timeout)
> 
> hm, would be nice to figure out what causes these IPIs. Could you stick 
> something like this into arch/x86/kernel/smp_32.c's 
> smp_send_reschedule() function [this is the function that generates the 
> IPI]:
> 
> static void native_smp_send_reschedule(int cpu)
> {
>         WARN_ON(cpu_is_offline(cpu));
>         send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR);
> 	if (panic_timeout > 0) {
> 		panic_timeout--;
> 		printk("IPI from task %s:%d on CPU#%d:\n", 
> 			current->comm, current->pid, cpu);
> 		dump_stack();
> 	}
> }
> 
> NOTE: if you run an SMP kernel then first remove these two lines from 
> kernel/printk.c:
> 
>         if (!oops_in_progress && waitqueue_active(&log_wait))
>                 wake_up_interruptible(&log_wait);
> 
> otherwise you'll get lockups. (the IPI is sent while holding the 
> runqueue lock, so the printks will lock up)
> 
> then wait for the bad condition to occur on your system and generate a 
> stream of ~10 backtraces, via:
> 
> 	echo 10 > /proc/sys/kernel/panic
> 
> you should be getting 10 immediate backtraces - please send them to us. 
> The backtraces should show the place that generates the wakeups. [turn 
> on CONFIG_FRAME_POINTERS=y to get high quality backtraces.]
>  
> If you do _not_ get 10 immediate backtraces, then something in the 
> system is generating such IPIs outside of the scheduler's control. That 
> would suggest some other sort of borkage.
> 
> 	Ingo

I grabbed the logs two times to make sure to catch needed info. 1st [1] one is generated while "Rescheduling interrupts" wakeups ~200 times and 2nd one generated for ~350 wakeups.

[1] http://cekirdek.pardus.org.tr/~caglar/dmesg.1st 
[2] http://cekirdek.pardus.org.tr/~caglar/dmesg.2nd

Cheers
-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 12:55   ` S.Çağlar Onur
@ 2008-01-22 15:23     ` Ingo Molnar
  2008-01-22 15:37       ` Ingo Molnar
  2008-01-22 15:55       ` S.Çağlar Onur
  0 siblings, 2 replies; 15+ messages in thread
From: Ingo Molnar @ 2008-01-22 15:23 UTC (permalink / raw)
  To: S.Çağlar Onur; +Cc: LKML, Arjan van de Ven


* S.Çağlar Onur <caglar@pardus.org.tr> wrote:

> I grabbed the logs two times to make sure to catch needed info. 1st [1] one is generated while "Rescheduling interrupts" wakeups ~200 times and 2nd one generated for ~350 wakeups.
> 
> [1] http://cekirdek.pardus.org.tr/~caglar/dmesg.1st 
> [2] http://cekirdek.pardus.org.tr/~caglar/dmesg.2nd

thanks, these seem to be mostly normal wakeups from standard tasks:

 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task X:2079 on CPU#1:
 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task hald-addon-inpu:2009 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task bash:2129 on CPU#0:
 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task events/0:7 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task bash:3902 on CPU#1:
 IPI from task bash:3902 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task X:2079 on CPU#0:
 IPI from task yakuake:3422 on CPU#0:
 IPI from task X:2079 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:

could you also add a similar IPI printouts (with the same panic_timeout 
logic) to arch/x86/kernel/smp_32.c's smp_reschedule_interrupt() function 
- while still keeping the other printouts too?

Could you also enable PRINTK_TIME timestamps, so that we can see the 
timings? (And do a "dmesg -n 1" so that the printks happen fast and the 
timings are accurate.) I'd suggest to increase CONFIG_LOG_BUF_SHIFT to 
20, so that your dmesg buffer is large enough. Plus try to capture 100 
events, ok?

My theory is that for whatever reason we get "repeat" IPIs: multiple 
reschedule IPIs although the other CPU only initiated one.

	Ingo

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 15:23     ` Ingo Molnar
@ 2008-01-22 15:37       ` Ingo Molnar
  2008-01-22 16:00         ` S.Çağlar Onur
  2008-01-22 15:55       ` S.Çağlar Onur
  1 sibling, 1 reply; 15+ messages in thread
From: Ingo Molnar @ 2008-01-22 15:37 UTC (permalink / raw)
  To: S.Çağlar Onur; +Cc: LKML, Arjan van de Ven


also, this might reduce the number of cross-CPU wakeups on near-idle 
systems:

  echo 1 > /sys/devices/system/cpu/sched_mc_power_savings

[ or if it doesnt, it should ;) ]

	Ingo

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 15:37       ` Ingo Molnar
@ 2008-01-22 16:00         ` S.Çağlar Onur
  0 siblings, 0 replies; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-22 16:00 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: LKML, Arjan van de Ven

Hi;

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı: 
> 
> also, this might reduce the number of cross-CPU wakeups on near-idle 
> systems:
> 
>   echo 1 > /sys/devices/system/cpu/sched_mc_power_savings
> 
> [ or if it doesnt, it should ;) ]
> 
> 	Ingo
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

Seems like nothing changes 


zangetsu ~ # cat /sys/devices/system/cpu/sched_mc_power_savings
1



Powertop still reports ~300 wakeups for "<kernel IPI> : Rescheduling interrupts"

     PowerTOP version 1.9       (C) 2007 Intel Corporation

Cn                Avg residency       P-states (frequencies)
C0 (cpu running)        ( 4,8%)
C1                0,0ms ( 0,0%)
C2                0,2ms ( 2,4%)
C3                2,4ms (92,8%)


Wakeups-from-idle per second : 495,2    interval: 3,0s
no ACPI power usage estimate available

Top causes for wakeups:
  40,0% (330,7)      <kernel IPI> : Rescheduling interrupts
  12,3% (102,0)   USB device  3-2 : HP Integrated Module (Broadcom Corp)
  12,1% (100,0)       <interrupt> : uhci_hcd:usb3
   8,0% ( 66,3)       <interrupt> : extra timer interrupt
   7,0% ( 58,0)         amarokapp : schedule_timeout (process_timeout)
   4,0% ( 33,0)       <interrupt> : uhci_hcd:usb2



and this is what system is doing while powertop reports above;

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.1  0.0   1512   532 ?        Ss   17:41   0:00 init [3]  
root         2  0.0  0.0      0     0 ?        S<   17:41   0:00 [kthreadd]
root         3  0.0  0.0      0     0 ?        S<   17:41   0:00 [migration/0]
root         4  0.0  0.0      0     0 ?        S<   17:41   0:00 [ksoftirqd/0]
root         5  0.0  0.0      0     0 ?        S<   17:41   0:00 [migration/1]
root         6  0.0  0.0      0     0 ?        S<   17:41   0:00 [ksoftirqd/1]
root         7  0.0  0.0      0     0 ?        S<   17:41   0:00 [events/0]
root         8  0.0  0.0      0     0 ?        S<   17:41   0:00 [events/1]
root         9  0.0  0.0      0     0 ?        S<   17:41   0:00 [khelper]
root        10  0.0  0.0      0     0 ?        S<   17:41   0:00 [kblockd/0]
root        11  0.0  0.0      0     0 ?        S<   17:41   0:00 [kblockd/1]
root        12  0.0  0.0      0     0 ?        S<   17:41   0:00 [kacpid]
root        13  0.0  0.0      0     0 ?        S<   17:41   0:00 [kacpi_notify]
root        14  0.0  0.0      0     0 ?        S<   17:41   0:00 [cqueue/0]
root        15  0.0  0.0      0     0 ?        S<   17:41   0:00 [cqueue/1]
root        16  0.0  0.0      0     0 ?        S<   17:41   0:00 [kseriod]
root        17  0.0  0.0      0     0 ?        S    17:41   0:00 [pdflush]
root        18  0.0  0.0      0     0 ?        S    17:41   0:00 [pdflush]
root        19  0.0  0.0      0     0 ?        S<   17:41   0:00 [kswapd0]
root        20  0.0  0.0      0     0 ?        S<   17:41   0:00 [aio/0]
root        21  0.0  0.0      0     0 ?        S<   17:41   0:00 [aio/1]
root        22  0.0  0.0      0     0 ?        S<   17:41   0:00 [kpsmoused]
root        42  0.0  0.0      0     0 ?        S<   17:41   0:00 [khpsbpkt]
root        46  0.0  0.0      0     0 ?        S<   17:41   0:00 [knodemgrd_0]
root        55  0.0  0.0      0     0 ?        S<   17:41   0:00 [ata/0]
root        56  0.0  0.0      0     0 ?        S<   17:41   0:00 [ata/1]
root        57  0.0  0.0      0     0 ?        S<   17:41   0:00 [ata_aux]
root        61  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_0]
root        62  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_1]
root        63  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_2]
root        64  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_3]
root        70  0.0  0.0      0     0 ?        S<   17:41   0:00 [ksuspend_usbd]
root        71  0.0  0.0      0     0 ?        S<   17:41   0:00 [khubd]
root        80  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_4]
root        81  0.0  0.0      0     0 ?        S<   17:41   0:00 [scsi_eh_5]
root       159  0.0  0.0      0     0 ?        S<   17:41   0:00 [kjournald]
root       194  0.0  0.0   2452  1304 ?        S<s  17:41   0:00 /sbin/udevd --daemon
root      1212  0.0  0.0      0     0 ?        S<   17:41   0:00 [kmmcd]
root      1378  0.0  0.0      0     0 ?        S<   17:41   0:00 [iwl3945/0]
root      1379  0.0  0.0      0     0 ?        S<   17:41   0:00 [iwl3945/1]
root      1408  0.0  0.0      0     0 ?        S<   17:41   0:00 [iwl3945]
root      1522  0.0  0.0   2320   348 ?        Ss   17:41   0:00 /usr/sbin/irqbalance
root      1554  0.0  0.0   3904  1200 ?        Ss   17:41   0:00 Comar         
root      1681  0.0  0.0   3904   720 ?        S    17:41   0:00 ComarRPC      
root      1693  0.0  0.0   1556   608 ?        Ss   17:41   0:00 /usr/sbin/syslogd -m 15
root      1696  0.0  0.0   1512   412 ?        Ss   17:41   0:00 /usr/sbin/klogd -c 3 -2
root      1697  0.0  0.0   2168   948 ?        Ss   17:41   0:00 /usr/sbin/hcid -s -f /etc/bluetooth/hcid.conf
root      1708  0.0  0.0      0     0 ?        S<   17:41   0:00 [krfcommd]
root      1726  0.0  0.0   2008   712 tty3     Ss+  17:41   0:00 /sbin/mingetty tty3
root      1727  0.0  0.0   2008   708 tty4     Ss+  17:41   0:00 /sbin/mingetty tty4
root      1728  0.0  0.0   2008   708 tty5     Ss+  17:41   0:00 /sbin/mingetty tty5
root      1729  0.0  0.0   2008   708 tty6     Ss+  17:41   0:00 /sbin/mingetty tty6
root      1730  0.0  0.0   1508   512 ?        Ss   17:41   0:00 /usr/sbin/acpid -c /etc/acpi/events
dbus      1797  0.0  0.0   2360  1000 ?        Ss   17:41   0:00 /usr/bin/dbus-daemon --system
root      1846  0.0  0.1   8384  2196 ?        Ssl  17:41   0:00 /usr/sbin/console-kit-daemon
hal       1939  0.0  0.1   5572  3948 ?        Ss   17:42   0:00 /usr/sbin/hald --daemon=yes --use-syslog
root      1943  0.0  0.0   2980  1080 ?        S    17:42   0:00 hald-runner
root      1950  0.5  1.7 214512 36420 ?        Ssl  17:42   0:04 /opt/sun-jdk/bin/java -DConfigFile=/opt/zemberek-server/config/conf.ini -Djava.library.path=/opt/zemberek-server/lib -Xverify:none -Xms12m -Xmx14m -jar /opt/zemberek-server/zemberek_server-0.7.jar
root      1951  0.0  0.0   1780   692 ?        Ss   17:42   0:00 /usr/sbin/cron
root      1952  0.0  0.0  10060   648 ?        S<sl 17:42   0:00 /sbin/auditd
root      1954  0.0  0.0   9828   648 ?        S<sl 17:42   0:00 /sbin/audispd
root      1955  0.0  0.0      0     0 ?        S<   17:42   0:00 [kauditd]
root      1962  0.0  0.1   5812  2088 ?        Ss   17:42   0:00 /usr/sbin/cupsd
avahi     1964  0.0  0.0   2656  1492 ?        Ss   17:42   0:00 avahi-daemon: running [zangetsu.local]
avahi     1967  0.0  0.0   2516   456 ?        Ss   17:42   0:00 avahi-daemon: chroot helper
root      2007  0.0  0.0   3072  1108 ?        S    17:42   0:00 hald-addon-input: Listening on /dev/input/event8 /dev/input/event9 /dev/input/event0 /dev/input/event4 /dev/input/event5 /dev/input/event6 /dev/input/event7
hal       2039  0.0  0.0   2032   888 ?        S    17:42   0:00 hald-addon-acpi: listening on acpid socket /var/run/acpid.socket
root      2044  0.0  0.0   3076  1024 ?        S    17:42   0:00 hald-addon-storage: polling /dev/sr0 (every 2 sec)
root      2057  0.0  0.0   1640   468 ?        Ss   17:42   0:00 /usr/sbin/avahi-dnsconfd -D
root      2071  0.0  0.0   3952   776 ?        Ss   17:42   0:00 /usr/kde/3.5/bin/kdm
root      2073  3.5  1.2  30852 26084 tty7     RLs+ 17:42   0:30 /usr/bin/X -br -nolisten tcp :0 vt7 -auth /var/run/xauth/A:0-E3nV3y
root      2077  0.0  0.0   4668  1976 ?        S    17:42   0:00 -:0                 
root      2080  0.0  0.0   3296  1360 ?        Ss   17:42   0:00 /usr/sbin/wpa_supplicant -wuB -P/var/run/wpa_supplicant.pid
root      2109  0.0  0.0   1652   248 ?        Ss   17:42   0:00 /sbin/dhcpcd -R -Y -N eth1 -t 120
root      2694  0.0  0.0   2008   708 tty2     Ss+  17:43   0:00 /sbin/mingetty --noclear tty2
root      2758  0.0  0.0   2008   708 tty1     Ss+  17:43   0:00 /sbin/mingetty --noclear tty1
caglar    2783  0.0  0.0   3016  1348 ?        Ss   17:43   0:00 /bin/sh /usr/kde/3.5/bin/startkde
caglar    2812  0.0  0.0   2664   468 ?        Ss   17:44   0:00 /usr/bin/gpg-agent --daemon
caglar    2815  0.0  0.0   3056   764 ?        Ss   17:44   0:00 /usr/bin/ssh-agent -s
caglar    2832  0.0  0.0   2984   432 ?        S    17:44   0:00 dbus-launch --sh-syntax --exit-with-session
caglar    2833  0.0  0.0   2228   864 ?        Ss   17:44   0:00 /usr/bin/dbus-daemon --fork --print-pid 5 --print-address 7 --session
root      2839  0.0  0.0   1360   148 ?        S    17:44   0:00 start_kdeinit --new-startup +kcminit_startup
caglar    2840  0.0  0.3  25008  7800 ?        Ss   17:44   0:00 kdeinit Running...                                                  
caglar    2843  0.0  0.1  24276  2788 ?        S    17:44   0:00 dcopserver [kdeinit] --nosid                                        
caglar    2845  0.0  0.3  26896  7720 ?        S    17:44   0:00 klauncher [kdeinit] --new-startup                                   
caglar    2847  0.0  0.7  33552 16424 ?        S    17:44   0:00 kded [kdeinit] --new-startup                                        
caglar    2852  0.0  0.0   1496   348 ?        S    17:44   0:00 kwrapper ksmserver
caglar    2854  0.0  0.4  26656  9392 ?        S    17:44   0:00 ksmserver [kdeinit]                                                 
caglar    2855  0.1  0.6  28584 12480 ?        S    17:44   0:01 kwin [kdeinit] -session 10dfd5e1dc000119905582800000074630008_1201  
caglar    2857  0.1  0.8  34436 17352 ?        S    17:44   0:01 kdesktop [kdeinit]                                                  
caglar    2859  0.1  0.8  45892 17384 ?        S    17:44   0:01 kicker [kdeinit]                                                    
caglar    2862  0.0  0.3  25560  6688 ?        S    17:44   0:00 kio_file [kdeinit] file /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    2866  0.0  0.3  13736  7856 ?        S    17:44   0:00 /usr/kde/3.5/bin/artsd -F 10 -S 4096 -s 3 -m artsmessage -c drkonqi -l 3 -f
caglar    2871  0.0  0.6  29552 12728 ?        S    17:44   0:00 kmix [kdeinit] -session 10dfd5e1dc000118109216400000036490013_1201  
caglar    2873  0.3  1.2  57188 26548 ?        S    17:44   0:02 akregator -session 10dfd5e1dc000119737236400000038700014_1201016429_751575
caglar    2876  0.0  0.5  25972 10908 ?        S    17:44   0:00 knazar -session 10dfd5e1dc000119738342100000051660022_1201016429_752054
caglar    2877  0.0  0.5  35540 11524 ?        S    17:44   0:00 knotify [kdeinit]                                                   
caglar    2879  0.0  0.7  41988 14848 ?        S    17:44   0:00 kgpg -session 10dfd5e1dc000119885454500000040010017_1201016429_751902
caglar    2881  0.4  0.7  29792 15976 ?        S    17:44   0:03 yakuake -session 10dfd5e1dc000119949009100000068430023_1201016429_752567
caglar    2882  3.5  2.7 152560 57376 ?        Sl   17:44   0:26 amarokapp -session 10dfd5e1dc000120001145300000022560015_1201016429_751762
caglar    2890  1.2  4.0 148500 83704 ?        Sl   17:44   0:09 kmail -session 10dfd5e1dc000120100924600000022060011_1201016429_752344
caglar    2894  0.0  0.5  27664 11080 ?        S    17:44   0:00 klipper [kdeinit]                                                   
caglar    2898  0.0  0.5  29504 11512 ?        S    17:44   0:00 kpowersave [kdeinit]                                                
caglar    3080  0.0  0.3  54032  7924 ?        S    17:44   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3081  0.0  0.3  53912  7916 ?        S    17:44   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3150  0.0  0.1   4136  2600 pts/2    Ss   17:44   0:00 /bin/bash
caglar    3236  0.0  0.4  16604  8576 ?        S    17:44   0:00 /usr/libexec/notification-daemon
caglar    3273  0.0  0.3  27164  7028 ?        S    17:44   0:00 kio_file [kdeinit] file /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3274  0.0  0.1   3692  2348 ?        S    17:44   0:00 ruby /usr/kde/3.5/share/apps/amarok/scripts/score_default/score_default.rb
caglar    3341  0.0  0.3  62224  8172 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3343  0.0  0.3  61208  8116 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3344  0.0  0.3  54036  8076 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3345  0.0  0.3  53012  8072 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3347  0.0  0.3  54040  8120 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3348  0.0  0.3  62232  8100 ?        S    17:46   0:00 kio_http [kdeinit] http /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
caglar    3897  0.0  0.8  56212 17004 ?        S    17:50   0:00 /usr/bin/python /usr/kde/3.5/bin/network-applet
caglar    4265  0.0  0.0   2752  1308 ?        S    17:53   0:00 /bin/sh /usr/bin/firefox
caglar    4267  1.1  1.6 131892 33644 ?        Sl   17:53   0:01 /usr/lib/MozillaFirefox//firefox-bin
caglar    4271  0.0  0.1   4148  2392 ?        S    17:53   0:00 /usr/libexec/gconfd-2 14
caglar    4300  0.0  0.4  54932  9120 ?        S    17:54   0:00 kio_pop3 [kdeinit] pop3 /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
root      4316  0.0  0.0   2524  1200 pts/2    S    17:55   0:00 su -
root      4318  0.2  0.1   4788  3476 pts/2    S    17:55   0:00 -su
root      4342  0.1  0.1   3200  2116 pts/2    S+   17:55   0:00 powertop
caglar    4345  0.1  0.1   4004  2540 pts/0    Ss   17:55   0:00 /bin/bash
root      4451  0.0  0.0   2524  1200 pts/0    S    17:55   0:00 su -
root      4453  0.3  0.1   4788  3448 pts/0    S    17:55   0:00 -su
caglar    4543  0.2  0.4  54064  9416 ?        S    17:55   0:00 kio_smtp [kdeinit] smtp /tmp/ksocket-caglar/klauncherTCaD9a.slave-  
root      4588  0.0  0.0   2272   964 pts/0    R+   17:56   0:00 ps aux

Cheers
-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 15:23     ` Ingo Molnar
  2008-01-22 15:37       ` Ingo Molnar
@ 2008-01-22 15:55       ` S.Çağlar Onur
  2008-01-22 16:05         ` Ingo Molnar
  1 sibling, 1 reply; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-22 15:55 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: LKML, Arjan van de Ven

Hi;

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı: 
> * S.Çağlar Onur <caglar@pardus.org.tr> wrote:
> > I grabbed the logs two times to make sure to catch needed info. 1st [1]
> > one is generated while "Rescheduling interrupts" wakeups ~200 times and
> > 2nd one generated for ~350 wakeups.
> >
> > [1] http://cekirdek.pardus.org.tr/~caglar/dmesg.1st
> > [2] http://cekirdek.pardus.org.tr/~caglar/dmesg.2nd
>
> thanks, these seem to be mostly normal wakeups from standard tasks:
>
>  IPI from task kdm_greet:2118 on CPU#0:
>  IPI from task X:2079 on CPU#1:
>  IPI from task kdm_greet:2118 on CPU#0:
>  IPI from task hald-addon-inpu:2009 on CPU#1:
>  IPI from task events/0:7 on CPU#1:
>  IPI from task bash:2129 on CPU#0:
>  IPI from task kdm_greet:2118 on CPU#0:
>  IPI from task events/0:7 on CPU#1:
>  IPI from task events/0:7 on CPU#1:
>  IPI from task events/0:7 on CPU#1:
>  IPI from task bash:3902 on CPU#1:
>  IPI from task bash:3902 on CPU#1:
>  IPI from task amarokapp:3423 on CPU#1:
>  IPI from task amarokapp:3423 on CPU#1:
>  IPI from task amarokapp:3423 on CPU#1:
>  IPI from task X:2079 on CPU#0:
>  IPI from task yakuake:3422 on CPU#0:
>  IPI from task X:2079 on CPU#1:
>  IPI from task amarokapp:3423 on CPU#1:
>  IPI from task amarokapp:3423 on CPU#1:
>
> could you also add a similar IPI printouts (with the same panic_timeout
> logic) to arch/x86/kernel/smp_32.c's smp_reschedule_interrupt() function
> - while still keeping the other printouts too?
>
> Could you also enable PRINTK_TIME timestamps, so that we can see the
> timings? (And do a "dmesg -n 1" so that the printks happen fast and the
> timings are accurate.) I'd suggest to increase CONFIG_LOG_BUF_SHIFT to
> 20, so that your dmesg buffer is large enough. Plus try to capture 100
> events, ok?
>
> My theory is that for whatever reason we get "repeat" IPIs: multiple
> reschedule IPIs although the other CPU only initiated one.

Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)

Cheers
-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 15:55       ` S.Çağlar Onur
@ 2008-01-22 16:05         ` Ingo Molnar
  2008-01-22 16:11           ` S.Çağlar Onur
                             ` (2 more replies)
  0 siblings, 3 replies; 15+ messages in thread
From: Ingo Molnar @ 2008-01-22 16:05 UTC (permalink / raw)
  To: S.Çağlar Onur; +Cc: LKML, Arjan van de Ven


* S.Çağlar Onur <caglar@pardus.org.tr> wrote:

> > My theory is that for whatever reason we get "repeat" IPIs: multiple 
> > reschedule IPIs although the other CPU only initiated one.
> 
> Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)

hm, the IPI sending and receiving is nicely paired up:

[  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
[  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:

amarokapp does wake up threads every 20 microseconds - that could 
explain it. It's probably Xorg running on one core, amarokapp on the 
other core. That's already 100 reschedules/sec.

	Ingo

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 16:05         ` Ingo Molnar
@ 2008-01-22 16:11           ` S.Çağlar Onur
  2008-01-22 16:22             ` S.Çağlar Onur
  2008-01-22 17:03           ` Matt Mackall
  2008-05-13 18:03           ` Vegard Nossum
  2 siblings, 1 reply; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-22 16:11 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: LKML, Arjan van de Ven

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı: 
> 
> * S.Çağlar Onur <caglar@pardus.org.tr> wrote:
> 
> > > My theory is that for whatever reason we get "repeat" IPIs: multiple 
> > > reschedule IPIs although the other CPU only initiated one.
> > 
> > Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)
> 
> hm, the IPI sending and receiving is nicely paired up:
> 
> [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
> [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:
> 
> amarokapp does wake up threads every 20 microseconds - that could 
> explain it. It's probably Xorg running on one core, amarokapp on the 
> other core. That's already 100 reschedules/sec.

Heh, killing amarok ends up with following;

     PowerTOP version 1.9       (C) 2007 Intel Corporation

Cn                Avg residency       P-states (frequencies)
C0 (cpu running)        ( 0,9%)
C1                0,0ms ( 0,0%)
C2                0,2ms ( 0,0%)
C3                5,1ms (99,1%)


Wakeups-from-idle per second : 197,8    interval: 10,0s
no ACPI power usage estimate available

Top causes for wakeups:
  34,7% (130,7)   USB device  3-2 : HP Integrated Module (Broadcom Corp)
  26,5% (100,0)       <interrupt> : uhci_hcd:usb3
   5,8% ( 22,0)              java : futex_wait (hrtimer_wakeup)
   5,3% ( 20,0)       <interrupt> : iwl3945
   4,1% ( 15,4)   USB device  2-2 : Microsoft Wireless Optical Mouse .00 (Microsoft)
   2,9% ( 11,0)       <interrupt> : libata
   2,7% ( 10,1)       <interrupt> : extra timer interrupt
   2,7% ( 10,0)              java : schedule_timeout (process_timeout)
   2,7% ( 10,0)     <kernel core> : scan_async (ehci_watchdog)
   2,4% (  9,0)      <kernel IPI> : Rescheduling interrupts
   2,1% (  8,0)   <kernel module> : usb_hcd_poll_rh_status (rh_timer_func)
   1,7% (  6,4)       <interrupt> : uhci_hcd:usb2
   1,7% (  6,4)             artsd : schedule_timeout (process_timeout)
   0,6% (  2,1)       <interrupt> : ohci1394, uhci_hcd:usb4, nvidia
   0,5% (  2,0)     <kernel core> : clocksource_check_watchdog (clocksource_watchdog)
   0,5% (  1,7)    wpa_supplicant : schedule_timeout (process_timeout)
   0,3% (  1,0)            kicker : schedule_timeout (process_timeout)
   0,3% (  1,0)              kwin : schedule_timeout (process_timeout)
   0,3% (  1,0)          kdesktop : schedule_timeout (process_timeout)
   0,3% (  1,0)           klipper : schedule_timeout (process_timeout)
   0,3% (  1,0)          kwrapper : do_nanosleep (hrtimer_wakeup)
   0,3% (  1,0)                 X : nv_start_rc_timer (nv_kern_rc_timer)

-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 16:11           ` S.Çağlar Onur
@ 2008-01-22 16:22             ` S.Çağlar Onur
  0 siblings, 0 replies; 15+ messages in thread
From: S.Çağlar Onur @ 2008-01-22 16:22 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: LKML, Arjan van de Ven

Hi;

22 Oca 2008 Sal tarihinde, S.Çağlar Onur şunları yazmıştı: 
> > hm, the IPI sending and receiving is nicely paired up:
> > 
> > [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
> > [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:
> > 
> > amarokapp does wake up threads every 20 microseconds - that could 
> > explain it. It's probably Xorg running on one core, amarokapp on the 
> > other core. That's already 100 reschedules/sec.
> 
> Heh, killing amarok ends up with following;
> 
>      PowerTOP version 1.9       (C) 2007 Intel Corporation
> 
> Cn                Avg residency       P-states (frequencies)
> C0 (cpu running)        ( 0,9%)
> C1                0,0ms ( 0,0%)
> C2                0,2ms ( 0,0%)
> C3                5,1ms (99,1%)
> 
> 
> Wakeups-from-idle per second : 197,8    interval: 10,0s
> no ACPI power usage estimate available
> 
> Top causes for wakeups:
>   34,7% (130,7)   USB device  3-2 : HP Integrated Module (Broadcom Corp)
>   26,5% (100,0)       <interrupt> : uhci_hcd:usb3
>    5,8% ( 22,0)              java : futex_wait (hrtimer_wakeup)
>    5,3% ( 20,0)       <interrupt> : iwl3945
>    4,1% ( 15,4)   USB device  2-2 : Microsoft Wireless Optical Mouse .00 (Microsoft)
>    2,9% ( 11,0)       <interrupt> : libata
>    2,7% ( 10,1)       <interrupt> : extra timer interrupt
>    2,7% ( 10,0)              java : schedule_timeout (process_timeout)
>    2,7% ( 10,0)     <kernel core> : scan_async (ehci_watchdog)
>    2,4% (  9,0)      <kernel IPI> : Rescheduling interrupts
>    2,1% (  8,0)   <kernel module> : usb_hcd_poll_rh_status (rh_timer_func)
>    1,7% (  6,4)       <interrupt> : uhci_hcd:usb2
>    1,7% (  6,4)             artsd : schedule_timeout (process_timeout)
>    0,6% (  2,1)       <interrupt> : ohci1394, uhci_hcd:usb4, nvidia
>    0,5% (  2,0)     <kernel core> : clocksource_check_watchdog (clocksource_watchdog)
>    0,5% (  1,7)    wpa_supplicant : schedule_timeout (process_timeout)
>    0,3% (  1,0)            kicker : schedule_timeout (process_timeout)
>    0,3% (  1,0)              kwin : schedule_timeout (process_timeout)
>    0,3% (  1,0)          kdesktop : schedule_timeout (process_timeout)
>    0,3% (  1,0)           klipper : schedule_timeout (process_timeout)
>    0,3% (  1,0)          kwrapper : do_nanosleep (hrtimer_wakeup)
>    0,3% (  1,0)                 X : nv_start_rc_timer (nv_kern_rc_timer)
 
By the way loging out from KDE also suffers same problem, this time kdm migrated to CPU1 and powertop reports ~300 wakeups for "<kernel IPI> : Rescheduling interrupts" again.

[...]
[ 2058.246692] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#0:
[ 2058.246737] IPI (@native_smp_send_reschedule) from task kdm_greet:6122 on CPU#1:
[ 2058.246812] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
[ 2058.278947] IPI (@native_smp_send_reschedule) from task X:2073 on CPU#0:
[ 2058.279070] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#0:
[ 2058.279175] IPI (@native_smp_send_reschedule) from task kdm_greet:6122 on CPU#1:
[ 2058.279251] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
[ 2058.279301] IPI (@native_smp_send_reschedule) from task X:2073 on CPU#0:
[ 2058.279377] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#0:
[ 2058.279425] IPI (@native_smp_send_reschedule) from task kdm_greet:6122 on CPU#1:
[ 2058.279503] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
[ 2058.279565] IPI (@native_smp_send_reschedule) from task X:2073 on CPU#0:
[ 2058.279637] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#0:
[ 2058.279683] IPI (@native_smp_send_reschedule) from task kdm_greet:6122 on CPU#1:
[ 2058.279758] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
[ 2058.311903] IPI (@native_smp_send_reschedule) from task X:2073 on CPU#0:
[ 2058.312028] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#0:
[...]

Cheers
-- 
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 16:05         ` Ingo Molnar
  2008-01-22 16:11           ` S.Çağlar Onur
@ 2008-01-22 17:03           ` Matt Mackall
  2008-01-22 19:27             ` Ingo Molnar
  2008-05-13 18:03           ` Vegard Nossum
  2 siblings, 1 reply; 15+ messages in thread
From: Matt Mackall @ 2008-01-22 17:03 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: S.Çağlar Onur, LKML, Arjan van de Ven


On Tue, 2008-01-22 at 17:05 +0100, Ingo Molnar wrote:
> * S.Çağlar Onur <caglar@pardus.org.tr> wrote:
> 
> > > My theory is that for whatever reason we get "repeat" IPIs: multiple 
> > > reschedule IPIs although the other CPU only initiated one.
> > 
> > Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)
> 
> hm, the IPI sending and receiving is nicely paired up:
> 
> [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:
> [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:
> 
> amarokapp does wake up threads every 20 microseconds - that could 
> explain it. It's probably Xorg running on one core, amarokapp on the 
> other core. That's already 100 reschedules/sec.

That suggests we want an "anti-load-balancing" heuristic when CPU usage
is very low. Migrating everything onto one core when we're close to idle
will save power and probably reduce latencies.

-- 
Mathematics is the supreme nostalgia of our time.


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 17:03           ` Matt Mackall
@ 2008-01-22 19:27             ` Ingo Molnar
       [not found]               ` <p73fxwoncs4.fsf@crumb.suse.de>
  0 siblings, 1 reply; 15+ messages in thread
From: Ingo Molnar @ 2008-01-22 19:27 UTC (permalink / raw)
  To: Matt Mackall; +Cc: S.Çağlar Onur, LKML, Arjan van de Ven

* Matt Mackall <mpm@selenic.com> wrote:

> > amarokapp does wake up threads every 20 microseconds - that could 
> > explain it. It's probably Xorg running on one core, amarokapp on the 
> > other core. That's already 100 reschedules/sec.
> 
> That suggests we want an "anti-load-balancing" heuristic when CPU 
> usage is very low. Migrating everything onto one core when we're close 
> to idle will save power and probably reduce latencies.

that would probably be the case if it's multiple sockets - but for 
multiple cores exactly the opposite is true: the sooner _both_ cores 
finish processing, the deeper power use the CPU can reach. So effective 
and immediate spreading of workloads amongst multiple cores - especially 
with shared L2 caches where the cost of migration is low, helps power 
consumption. (and it obviously helps latencies and bandwith)

	Ingo

^ permalink raw reply	[flat|nested] 15+ messages in thread

[parent not found: <p73fxwoncs4.fsf@crumb.suse.de>]

* Re: Rescheduling interrupts
       [not found]               ` <p73fxwoncs4.fsf@crumb.suse.de>
@ 2008-01-23 15:52                 ` Matt Mackall
  0 siblings, 0 replies; 15+ messages in thread
From: Matt Mackall @ 2008-01-23 15:52 UTC (permalink / raw)
  To: Andi Kleen; +Cc: Ingo Molnar, S.Çağlar Onur, LKML, Arjan van de Ven


On Wed, 2008-01-23 at 09:53 +0100, Andi Kleen wrote:
> Ingo Molnar <mingo@elte.hu> writes:
> 
> > that would probably be the case if it's multiple sockets - but for 
> > multiple cores exactly the opposite is true: the sooner _both_ cores 
> > finish processing, the deeper power use the CPU can reach. 
> 
> That's only true on setups where the cores don't have 
> separate sleep states. But that's not generally true anymore.
> e.g. AMD Fam10h has completely separate power planes for
> the cores and I believe newer Intel CPUs can also let their 
> cores go to at least some sleep states independently (although
> the deepest sleep modi still require all cores idle) 

I think we can expect everyone to rapidly evolve towards full
independence of core power states. In fact, it wouldn't surprise me if
we eventually get to the point of shutting down individual functional
units like the FPU.

-- 
Mathematics is the supreme nostalgia of our time.


^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-01-22 16:05         ` Ingo Molnar
  2008-01-22 16:11           ` S.Çağlar Onur
  2008-01-22 17:03           ` Matt Mackall
@ 2008-05-13 18:03           ` Vegard Nossum
  2008-05-13 19:04             ` Vegard Nossum
  2 siblings, 1 reply; 15+ messages in thread
From: Vegard Nossum @ 2008-05-13 18:03 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: S.Çağlar Onur, LKML, Arjan van de Ven

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Hi,
On Tue, Jan 22, 2008 at 6:05 PM, Ingo Molnar <mingo@elte.hu> wrote:>>  * S.Ã‡aÄŸlar Onur <caglar@pardus.org.tr> wrote:>>> > > My theory is that for whatever reason we get "repeat" IPIs: multiple>  > > reschedule IPIs although the other CPU only initiated one.>  >>  > Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)>>  hm, the IPI sending and receiving is nicely paired up:>>  [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:>  [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:>>  amarokapp does wake up threads every 20 microseconds - that could>  explain it. It's probably Xorg running on one core, amarokapp on the>  other core. That's already 100 reschedules/sec.
Was this IPI thing ever resolved/fixed? I'm seeing the exact samething on my newest Fedora 8 kernel (2.6.24.5-85.fc8) now:
  33.3% (334.0)      <kernel IPI> : Rescheduling interrupts
And I know for sure that this did not show up a couple of months back.
If the cause of this is known, please let me know about it. If itisn't, I will start a bisect run now :-)
Thanks.

Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in whilethe programmer was not looking is intellectually dishonest as itdisguises that the error is the programmer's own creation."	-- E. W. Dijkstra, EWD1036ÿôèº{.nÇ+‰·Ÿ®‰†+%ŠËÿ±éÝ¶\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dÊ‡Ú™ë,j\a¢f£¢·hšïêÿ‘êçz_è®\x03(éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨èÚ&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

^ permalink raw reply	[flat|nested] 15+ messages in thread

* Re: Rescheduling interrupts
  2008-05-13 18:03           ` Vegard Nossum
@ 2008-05-13 19:04             ` Vegard Nossum
  0 siblings, 0 replies; 15+ messages in thread
From: Vegard Nossum @ 2008-05-13 19:04 UTC (permalink / raw)
  To: Ingo Molnar; +Cc: S.Çağlar Onur, LKML, Arjan van de Ven

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On Tue, May 13, 2008 at 8:03 PM, Vegard Nossum <vegard.nossum@gmail.com> wrote:> Hi,>>>  On Tue, Jan 22, 2008 at 6:05 PM, Ingo Molnar <mingo@elte.hu> wrote:>  >>  >  * S.Ã‡aÄŸlar Onur <caglar@pardus.org.tr> wrote:>  >>  >>  > > > My theory is that for whatever reason we get "repeat" IPIs: multiple>  >  > > reschedule IPIs although the other CPU only initiated one.>  >  >>  >  > Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)>  >>  >  hm, the IPI sending and receiving is nicely paired up:>  >>  >  [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:>  >  [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:>  >>  >  amarokapp does wake up threads every 20 microseconds - that could>  >  explain it. It's probably Xorg running on one core, amarokapp on the>  >  other core. That's already 100 reschedules/sec.>>  Was this IPI thing ever resolved/fixed? I'm seeing the exact same>  thing on my newest Fedora 8 kernel (2.6.24.5-85.fc8) now:>>   33.3% (334.0)      <kernel IPI> : Rescheduling interrupts>>  And I know for sure that this did not show up a couple of months back.>>  If the cause of this is known, please let me know about it. If it>  isn't, I will start a bisect run now :-)
Ok -- just a confirmation. I have this on v2.6.26-rc1:
Running only init=/bin/sh (from busybox) and powertop shows:kernel IPI : Rescheduling interrupts
completely idle box (except powertop): 1 wakeups/secone busy-loop[1]: 2 wakeups/sectwo busy-loops: 500 wakeups/sec
So it seems like a real bug to me.

Vegard
[1]: while true; do echo hi; done
-- "The animistic metaphor of the bug that maliciously sneaked in whilethe programmer was not looking is intellectually dishonest as itdisguises that the error is the programmer's own creation."	-- E. W. Dijkstra, EWD1036ÿôèº{.nÇ+‰·Ÿ®‰†+%ŠËÿ±éÝ¶\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dÊ‡Ú™ë,j\a¢f£¢·hšïêÿ‘êçz_è®\x03(éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨èÚ&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

^ permalink raw reply	[flat|nested] 15+ messages in thread

end of thread, other threads:[~2008-05-13 19:04 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-01-21 23:19 Rescheduling interrupts S.Çağlar Onur
2008-01-22 10:57 ` Ingo Molnar
2008-01-22 12:55   ` S.Çağlar Onur
2008-01-22 15:23     ` Ingo Molnar
2008-01-22 15:37       ` Ingo Molnar
2008-01-22 16:00         ` S.Çağlar Onur
2008-01-22 15:55       ` S.Çağlar Onur
2008-01-22 16:05         ` Ingo Molnar
2008-01-22 16:11           ` S.Çağlar Onur
2008-01-22 16:22             ` S.Çağlar Onur
2008-01-22 17:03           ` Matt Mackall
2008-01-22 19:27             ` Ingo Molnar
     [not found]               ` <p73fxwoncs4.fsf@crumb.suse.de>
2008-01-23 15:52                 ` Matt Mackall
2008-05-13 18:03           ` Vegard Nossum
2008-05-13 19:04             ` Vegard Nossum

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