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Date: Thu, 30 Oct 2008 19:00:31 -0700
From: Venki Pallipadi <venkatesh.pallipadi@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel <linux-kernel@...r.kernel.org>
Subject: nohz regression with upstream git
Thomas,
I am seeing a nohz regression on one of my dual core mobile test boxes.
With 2.6.27 tickless idle works fine.
With latest git, I see ~2000 interrupts per second (HZ=1000), even when idle.
git bisect points towards
commit fb02fbc14d17837b4b7b02dbb36142c16a7bf208
Author: Thomas Gleixner <tglx@...utronix.de>
Date: Fri Oct 17 10:01:23 2008 +0200
NOHZ: restart tick device from irq_enter()
And good powertop data
PowerTOP 1.10 (C) 2007, 2008 Intel Corporation
Collecting data for 15 seconds
Cn Avg residency
C0 (cpu running) ( 0.1%)
polling 0.0ms ( 0.0%)
C1 0.0ms ( 0.0%)
C3 18.6ms (99.9%)
P-states (frequencies)
2.21 Ghz 0.0%
2.21 Ghz 0.0%
1.60 Ghz 0.0%
800 Mhz 100.0%
Wakeups-from-idle per second : 53.9 interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
65.5% ( 32.6) <interrupt> : extra timer interrupt
16.7% ( 8.3) <kernel IPI> : Rescheduling interrupts
3.3% ( 1.7) kacpid : schedule_timeout (process_timeout)
2.8% ( 1.4) <interrupt> : ata_piix, uhci_hcd:usb4
2.3% ( 1.1) <interrupt> : eth1
2.0% ( 1.0) <kernel core> : enqueue_task_rt (sched_rt_period_timer)
1.9% ( 0.9) <kernel core> : schedule_delayed_work_on (delayed_work_timer_fn)
1.1% ( 0.5) <kernel core> : neigh_table_init_no_netlink (neigh_periodic_timer)
1.1% ( 0.5) <kernel core> : e1000_intr_msi (e1000_watchdog)
0.7% ( 0.3) <kernel IPI> : Function call interrupts
0.4% ( 0.2) events/1 : __netdev_watchdog_up (dev_watchdog)
0.4% ( 0.2) sendmail : schedule_timeout (process_timeout)
0.4% ( 0.2) <kernel core> : page_writeback_init (wb_timer_fn)
0.3% ( 0.1) kerneloops : schedule_timeout (process_timeout)
0.3% ( 0.1) kerneloops : do_nanosleep (hrtimer_wakeup)
0.1% ( 0.1) sshd : sk_reset_timer (tcp_write_timer)
0.1% ( 0.1) events/1 : queue_delayed_work (delayed_work_timer_fn)
0.1% ( 0.1) mount : start_this_handle (commit_timeout)
0.1% ( 0.1) <kernel core> : queue_delayed_work (delayed_work_timer_fn)
0.1% ( 0.1) hald-addon-stor : schedule_timeout (process_timeout)
0.1% ( 0.1) <kernel core> : neigh_add_timer (neigh_timer_handler)
0.1% ( 0.1) <kernel core> : sk_reset_timer (tcp_delack_timer)
and bad powertop data
PowerTOP 1.10 (C) 2007, 2008 Intel Corporation
Collecting data for 15 seconds
Cn Avg residency
C0 (cpu running) ( 5.6%)
polling 0.0ms ( 0.0%)
C1 1.2ms ( 0.0%)
C3 0.5ms (94.4%)
P-states (frequencies)
2.21 Ghz 0.0%
2.21 Ghz 0.0%
1.60 Ghz 0.0%
800 Mhz 100.0%
Wakeups-from-idle per second : 1919.6 interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
99.0% (1902.4) <interrupt> : extra timer interrupt
0.3% ( 6.1) <kernel IPI> : Rescheduling interrupts
0.3% ( 5.6) <interrupt> : acpi
0.1% ( 1.4) <interrupt> : ata_piix, uhci_hcd:usb4
0.1% ( 1.1) <interrupt> : ata_piix, ehci_hcd:usb1, uhci_hcd:usb6
0.1% ( 1.1) <interrupt> : eth1
0.1% ( 1.0) <kernel core> : enqueue_task_rt (sched_rt_period_timer)
0.0% ( 0.9) <kernel core> : schedule_delayed_work_on (delayed_work_timer_fn)
0.0% ( 0.5) NetworkManager : e1000_intr_msi (e1000_watchdog)
0.0% ( 0.5) <kernel core> : neigh_table_init_no_netlink (neigh_periodic_timer)
0.0% ( 0.2) <kernel core> : page_writeback_init (wb_timer_fn)
0.0% ( 0.2) events/1 : __netdev_watchdog_up (dev_watchdog)
0.0% ( 0.2) sendmail : schedule_timeout (process_timeout)
0.0% ( 0.1) kerneloops : schedule_timeout (process_timeout)
0.0% ( 0.1) events/0 : sk_reset_timer (tcp_delack_timer)
0.0% ( 0.1) sshd : sk_reset_timer (tcp_write_timer)
0.0% ( 0.1) events/0 : neigh_add_timer (neigh_timer_handler)
0.0% ( 0.1) rsyslogd : schedule_timeout (process_timeout)
0.0% ( 0.1) rpcbind : schedule_timeout (process_timeout)
0.0% ( 0.1) mount : start_this_handle (commit_timeout)
0.0% ( 0.1) hald : schedule_timeout (process_timeout)
0.0% ( 0.1) crond : do_nanosleep (hrtimer_wakeup)
0.0% ( 0.1) <kernel core> : queue_delayed_work (delayed_work_timer_fn)
0.0% ( 0.1) hald-addon-stor : schedule_timeout (process_timeout)
Not sure what is so specific about this platform that causes this problem.
Its a regular Centrino 2 development box.
I will poke more at this tomorrow. But, wanted to pass the info on to you
before calling it a night.
Let me know if you need any more info on this.
Thanks,
Venki
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