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From: "=?utf-8?q?S=2E=C3=87a=C4=9Flar?= Onur" <caglar@pardus.org.tr>
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To: Ingo Molnar <mingo@elte.hu>
Subject: Re: Rescheduling interrupts
Date: Tue, 22 Jan 2008 18:22:04 +0200
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Cc: LKML <linux-kernel@vger.kernel.org>,
       Arjan van de Ven <arjan@linux.intel.com>
References: <200801220119.42312.caglar@pardus.org.tr> <20080122160557.GA31831@elte.hu> <200801221811.25867.caglar@pardus.org.tr>
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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!
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