linux-kernel - Re: Rescheduling interrupts

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Date:	Tue, 22 Jan 2008 18:11:24 +0200
From:	"S.Çağlar Onur" <caglar@...dus.org.tr>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: Rescheduling interrupts

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı: 
> 
> * S.Çağlar Onur <caglar@...dus.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@...dus.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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