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SubjectRe: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove_hrtimer
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Date
Peter and tglx,

About which hrtimer causes the performance issue, I did some test with my home server because I am on vacation, An ASUS PC server with 4 core Intel i5 cpu inside,
Running the Stable 3.11RC3+ (removed reschedule IPI), almost got the same result as I did with Sun Servers. I suspect it is the tick_sched_timer, the evidence as following:
While running some test tools such as http://people.redhat.com/mingo/cfs-scheduler/tools/pipe-test-1m.c, the powertop
tool shows following result:

PowerTOP version 1.11 (C) 2007 Intel Corporation

Cn Avg residency P-states (frequencies)
C0 (cpu running) ( 2.2%) Turbo Mode 0.0%
polling 0.0ms ( 0.0%) 3.21 Ghz 0.0%
C1 mwait 0.6ms ( 0.9%) 3.10 Ghz 0.0%
C2 mwait 0.5ms ( 0.1%) 3.00 Ghz 0.0%
C3 mwait 0.9ms (96.7%) 1.60 Ghz 100.0%

Wakeups-from-idle per second : 1100.9 interval: 0.3s
no ACPI power usage estimate available

Top causes for wakeups:
23.5% ( inf) swapper/3 : hrtimer_start_range_ns (tick_sched_timer)
23.5% ( inf) swapper/0 : hrtimer_start_range_ns (tick_sched_timer)
23.5% ( inf) swapper/2 : hrtimer_start_range_ns (tick_sched_timer)
23.5% ( inf) swapper/1 : hrtimer_start_range_ns (tick_sched_timer)
2.4% ( inf) <interrupt> : xhci_hcd
2.4% ( inf) USB device 3-4 : Basic Optical Mouse (Microsoft)
0.3% ( inf) rcu_sched : rcu_gp_kthread (process_timeout)
0.2% ( inf) gnome-terminal : hrtimer_start_range_ns (hrtimer_wakeup)
0.2% ( inf) <interrupt> : PS/2 keyboard/mouse/touchpad
0.1% ( inf) swapper/0 : hrtimer_start (menu_hrtimer_notify)
0.1% ( inf) swapper/0 : clocksource_watchdog
(clocksource_watchdog)
0.1% ( inf) cimserver : hrtimer_start_range_ns (hrtimer_wakeup)
0.1% ( inf) avahi-daemon : hrtimer_start_range_ns (hrtimer_wakeup)
0.1% ( inf) kworker/0:1 : queue_delayed_work_on
(delayed_work_timer_fn)
0.1% ( inf) rtkit-daemon : hrtimer_start_range_ns (hrtimer_wakeup)

And the /proc/timers_list

[root@localhost proc]# cat timer_list
Timer List Version: v0.7
HRTIMER_MAX_CLOCK_BASES: 4
now at 1463485951666 nsecs

cpu: 0
clock 0:
.base: ffff88021ea0d2c0
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: <ffff88021ea0d780>, tick_sched_timer, S:01, hrtimer_start_range_ns, swapper/0/1
# expires at 1463486000000-1463486000000 nsecs [in 48507 to 48507 nsecs]
#1: <ffff88021ea0d900>, watchdog_timer_fn, S:01, hrtimer_start, watchdog/0/10
# expires at 1464038000000-1464038000000 nsecs [in 552048507 to 552048507 nsecs]
#2: <ffff880215b139d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, gnome-power-man/7341
# expires at 1467041141813-1467051131812 nsecs [in 3555190320 to 3565180319 nsecs]
#3: <ffff8802118eb8c8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, ntpd/6806
# expires at 1469048348291-1469061256427 nsecs [in 5562396798 to 5575304934 nsecs]
#4: <ffff88020f34b8c8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, cimservermain/6993
# expires at 1521114040522-1521214040522 nsecs [in 57628089029 to 57728089029 nsecs]
#5: <ffff880215b57d78>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, master/6886
# expires at 1521833602390-1521892602389 nsecs [in 58347650897 to 58406650896 nsecs]
#6: <ffff880213c9c238>, it_real_fn, S:01, hrtimer_start, master/6886
# expires at 1795833601062-1795833601062 nsecs [in 332347649569 to 332347649569 nsecs]
clock 1:
.base: ffff88021ea0d300
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1375508485789320552 nsecs
active timers:
#0: <ffff8802157e5e28>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, automount/6767
# expires at 1375509966602894000-1375509966602944000 nsecs [in 1375508503116942507 to 1375508503116992507 nsecs]
clock 2:
.base: ffff88021ea0d340
.index: 2
.resolution: 1 nsecs
.get_time: ktime_get_boottime
.offset: 0 nsecs
active timers:
clock 3:
.base: ffff88021ea0d380
.index: 3
.resolution: 1 nsecs
.get_time: ktime_get_clocktai
.offset: 1375508485789320552 nsecs
active timers:
.expires_next : 1463487000000 nsecs
.hres_active : 1
.nr_events : 1489177
.nr_retries : 145
.nr_hangs : 0
.max_hang_time : 0 nsecs
.nohz_mode : 0
.last_tick : 0 nsecs
.tick_stopped : 0
.idle_jiffies : 0
.idle_calls : 0
.idle_sleeps : 0
.idle_entrytime : 0 nsecs
.idle_waketime : 0 nsecs
.idle_exittime : 0 nsecs
.idle_sleeptime : 0 nsecs
.iowait_sleeptime: 0 nsecs
.last_jiffies : 0
.next_jiffies : 0
.idle_expires : 0 nsecs
jiffies: 4296130782

cpu: 1
clock 0:
.base: ffff88021ea8d2c0
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: <ffff88021ea8d780>, tick_sched_timer, S:01, hrtimer_start_range_ns, swapper/1/0
# expires at 1463487000000-1463487000000 nsecs [in 1048507 to 1048507 nsecs]
#1: <ffff88021ea8d900>, watchdog_timer_fn, S:01, hrtimer_start, watchdog/1/11
# expires at 1464038000000-1464038000000 nsecs [in 552048507 to 552048507 nsecs]
#2: <ffff88020e2739d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, hald-addon-stor/6726
# expires at 1464211071890-1464213064889 nsecs [in 725120397 to 727113396 nsecs]
#3: <ffff8802157c99d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, rtkit-daemon/7358
# expires at 1467525043210-1467530043209 nsecs [in 4039091717 to 4044091716 nsecs]
#4: <ffff880213ec19d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, rtkit-daemon/7359
# expires at 1472525038227-1472525038227 nsecs [in 9039086734 to 9039086734 nsecs]
#5: <ffff880211a29ea8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, crond/6941
# expires at 1475497502106-1475497552106 nsecs [in 12011550613 to 12011600613 nsecs]
#6: <ffff88021519d9d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, hald/6673
# expires at 1490211101222-1490241071221 nsecs [in 26725149729 to 26755119728 nsecs]
#7: <ffff880215055d78>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, certmonger/7048
# expires at 1492497024071-1492527024070 nsecs [in 29011072578 to 29041072577 nsecs]
#8: <ffff88021182d8c8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, rsyslogd/6412
# expires at 86416926181907-86417026181907 nsecs [in 84953440230414 to 84953540230414 nsecs]
clock 1:
.base: ffff88021ea8d300
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1375508485789320552 nsecs
active timers:
clock 2:
.base: ffff88021ea8d340
.index: 2
.resolution: 1 nsecs
.get_time: ktime_get_boottime
.offset: 0 nsecs
active timers:
clock 3:
.base: ffff88021ea8d380
.index: 3
.resolution: 1 nsecs
.get_time: ktime_get_clocktai
.offset: 1375508485789320552 nsecs
active timers:
.expires_next : 1463487000000 nsecs
.hres_active : 1
.nr_events : 1505848
.nr_retries : 273
.nr_hangs : 0
.max_hang_time : 0 nsecs
.nohz_mode : 0
.last_tick : 0 nsecs
.tick_stopped : 0
.idle_jiffies : 0
.idle_calls : 0
.idle_sleeps : 0
.idle_entrytime : 0 nsecs
.idle_waketime : 0 nsecs
.idle_exittime : 0 nsecs
.idle_sleeptime : 0 nsecs
.iowait_sleeptime: 0 nsecs
.last_jiffies : 0
.next_jiffies : 0
.idle_expires : 0 nsecs
jiffies: 4296130782

cpu: 2
clock 0:
.base: ffff88021eb0d2c0
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: <ffff88021eb0d780>, tick_sched_timer, S:01, hrtimer_start_range_ns, swapper/2/0
# expires at 1463487000000-1463487000000 nsecs [in 1048507 to 1048507 nsecs]
#1: <ffff880213f918c8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, cimserver/6992
# expires at 1463603820300-1463604070299 nsecs [in 117868807 to 118118806 nsecs]
#2: <ffff88021eb0d900>, watchdog_timer_fn, S:01, hrtimer_start, watchdog/2/16
# expires at 1464050000000-1464050000000 nsecs [in 564048507 to 564048507 nsecs]
#3: <ffff8802156939d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, gnome-settings-/7329
# expires at 1467041063935-1467045059934 nsecs [in 3555112442 to 3559108441 nsecs]
#4: <ffff880214db39d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, gconfd-2/7310
# expires at 1467041085986-1467071055985 nsecs [in 3555134493 to 3585104492 nsecs]
#5: <ffff88020fb41ea8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, irqbalance/6442
# expires at 1468210681330-1468210731330 nsecs [in 4724729837 to 4724779837 nsecs]
#6: <ffff880211a5f9d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, rpcbind/6461
# expires at 1488949026351-1488979026350 nsecs [in 25463074858 to 25493074857 nsecs]
#7: <ffff8802141ed9d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, NetworkManager/6495
# expires at 1518210833956-1518310833956 nsecs [in 54724882463 to 54824882463 nsecs]
#8: <ffff88021492bd78>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, qmgr/6899
# expires at 1521592237483-1521692237483 nsecs [in 58106285990 to 58206285990 nsecs]
#9: <ffff880214a929b8>, it_real_fn, S:01, hrtimer_start, qmgr/6899
# expires at 1554592221196-1554592221196 nsecs [in 91106269703 to 91106269703 nsecs]
#10: <ffff880212685ea8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, atd/6952
# expires at 3620649306705-3620649356705 nsecs [in 2157163355212 to 2157163405212 nsecs]
clock 1:
.base: ffff88021eb0d300
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1375508485789320552 nsecs
active timers:
clock 2:
.base: ffff88021eb0d340
.index: 2
.resolution: 1 nsecs
.get_time: ktime_get_boottime
.offset: 0 nsecs
active timers:
clock 3:
.base: ffff88021eb0d380
.index: 3
.resolution: 1 nsecs
.get_time: ktime_get_clocktai
.offset: 1375508485789320552 nsecs
active timers:
.expires_next : 1463487000000 nsecs
.hres_active : 1
.nr_events : 1499325
.nr_retries : 236
.nr_hangs : 0
.max_hang_time : 0 nsecs
.nohz_mode : 0
.last_tick : 0 nsecs
.tick_stopped : 0
.idle_jiffies : 0
.idle_calls : 0
.idle_sleeps : 0
.idle_entrytime : 0 nsecs
.idle_waketime : 0 nsecs
.idle_exittime : 0 nsecs
.idle_sleeptime : 0 nsecs
.iowait_sleeptime: 0 nsecs
.last_jiffies : 0
.next_jiffies : 0
.idle_expires : 0 nsecs
jiffies: 4296130782

cpu: 3
clock 0:
.base: ffff88021eb8d2c0
.index: 0
.resolution: 1 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: <ffff88021eb8d780>, tick_sched_timer, S:01, hrtimer_start_range_ns, swapper/3/0
# expires at 1463487000000-1463487000000 nsecs [in 1048507 to 1048507 nsecs]
#1: <ffff88021eb8d900>, watchdog_timer_fn, S:01, hrtimer_start, watchdog/3/21
# expires at 1464062000000-1464062000000 nsecs [in 576048507 to 576048507 nsecs]
#2: <ffff880215b199d8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, gdm-simple-gree/7340
# expires at 1474212089328-1474272025327 nsecs [in 10726137835 to 10786073834 nsecs]
#3: <ffff88021402dea8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, sleep/7669
# expires at 1520896517118-1520896567118 nsecs [in 57410565625 to 57410615625 nsecs]
#4: <ffff880214befd78>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, pickup/6898
# expires at 1562833597553-1562933597552 nsecs [in 99347646060 to 99447646059 nsecs]
#5: <ffff88021277d8c8>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, Xorg/7216
# expires at 1826170099331-1826270099331 nsecs [in 362684147838 to 362784147838 nsecs]
#6: <ffff880214cda9b8>, it_real_fn, S:01, hrtimer_start, pickup/6898
# expires at 7462833595405-7462833595405 nsecs [in 5999347643912 to 5999347643912 nsecs]
clock 1:
.base: ffff88021eb8d300
.index: 1
.resolution: 1 nsecs
.get_time: ktime_get_real
.offset: 1375508485789320552 nsecs
active timers:
#0: <ffff880212e1de28>, hrtimer_wakeup, S:01, hrtimer_start_range_ns, cimservermain/6997
# expires at 1375509967695245000-1375509967695295000 nsecs [in 1375508504209293507 to 1375508504209343507 nsecs]
clock 2:
.base: ffff88021eb8d340
.index: 2
.resolution: 1 nsecs
.get_time: ktime_get_boottime
.offset: 0 nsecs
active timers:
clock 3:
.base: ffff88021eb8d380
.index: 3
.resolution: 1 nsecs
.get_time: ktime_get_clocktai
.offset: 1375508485789320552 nsecs
active timers:
.expires_next : 1463487000000 nsecs
.hres_active : 1
.nr_events : 1490001
.nr_retries : 347
.nr_hangs : 0
.max_hang_time : 0 nsecs
.nohz_mode : 0
.last_tick : 0 nsecs
.tick_stopped : 0
.idle_jiffies : 0
.idle_calls : 0
.idle_sleeps : 0
.idle_entrytime : 0 nsecs
.idle_waketime : 0 nsecs
.idle_exittime : 0 nsecs
.idle_sleeptime : 0 nsecs
.iowait_sleeptime: 0 nsecs
.last_jiffies : 0
.next_jiffies : 0
.idle_expires : 0 nsecs
jiffies: 4296130782

Tick Device: mode: 1
Broadcast device
Clock Event Device: hpet
max_delta_ns: 149983013276
min_delta_ns: 13409
mult: 61496111
shift: 32
mode: 1
next_event: 9223372036854775807 nsecs
set_next_event: hpet_legacy_next_event
set_mode: hpet_legacy_set_mode
event_handler: tick_handle_oneshot_broadcast
retries: 0

tick_broadcast_mask: 00000000
tick_broadcast_oneshot_mask: 00000000

Tick Device: mode: 1
Per CPU device: 0
Clock Event Device: lapic
max_delta_ns: 1377930800842
min_delta_ns: 1000
mult: 13387279
shift: 27
mode: 3
next_event: 1463487000000 nsecs
set_next_event: lapic_next_deadline
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
retries: 0

Tick Device: mode: 1
Per CPU device: 1
Clock Event Device: lapic
max_delta_ns: 1377930800842
min_delta_ns: 1000
mult: 13387279
shift: 27
mode: 3
next_event: 1463487000000 nsecs
set_next_event: lapic_next_deadline
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
retries: 1

Tick Device: mode: 1
Per CPU device: 2
Clock Event Device: lapic
max_delta_ns: 1377930800842
min_delta_ns: 1000
mult: 13387279
shift: 27
mode: 3
next_event: 1463487000000 nsecs
set_next_event: lapic_next_deadline
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
retries: 0

Tick Device: mode: 1
Per CPU device: 3
Clock Event Device: lapic
max_delta_ns: 1377930800842
min_delta_ns: 1000
mult: 13387279
shift: 27
mode: 3
next_event: 1463487000000 nsecs
set_next_event: lapic_next_deadline
set_mode: lapic_timer_setup
event_handler: hrtimer_interrupt
retries: 0

Note, I removed the reshcedule IPI for test reason, or reschedule IPI is the first reason to wake-up (In another mail I will tell why I removed the reschedule IPI).
The tick_sched_timers are issued by:

cpu_idle_loop() => tick_nohz_idle_enter() = > tick_nohz_stop_sched_tick() = > raise_softirq_irqoff(TIMER_SOFTIRQ)----------------------------------->+
run_timer_softirq() => tick_sched_timer()=> tick_sched_handle()=>update_process_times()=> run_local_timers() =>raise_softirq_irqoff(TIMER_SOFTIRQ)-->+
^----------------------------------------------------------------------------------------------------------------------------------------------------<

Thanks,
Ethan



在 2013-7-30,下午7:59,Peter Zijlstra <peterz@infradead.org> 写道:

> On Tue, Jul 30, 2013 at 07:44:03PM +0800, Ethan Zhao wrote:
>> Got it.
>> what tglx and you mean
>>
>>
>> So the expensive thing maybe not inside the schedule(), but could
>> outside the scheduler(), the more bigger forever loop.
>>
>> This is one part of what I am facing.
>
> Right, so it would be good if you could further diagnose the problem so
> we can come up with a solution that cures the problem while retaining
> the current 'desired' properties.
>
> The patch you pinpointed caused a regression in that it would wake from
> NOHZ mode far too often. Could it be that the now longer idle sections
> cause your CPU to go into deeper idle modes and you're suffering from
> idle-exit latencies?

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