linux-kernel - Rescheduling interrupts

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Date:	Tue, 22 Jan 2008 01:19:38 +0200
From:	"S.Çağlar Onur" <caglar@...dus.org.tr>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Rescheduling interrupts

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@...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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