Re: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove_hrtimer

From: ethan.zhao
Date: Thu Aug 08 2013 - 00:32:10 EST

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Hi, perter and Mike,

Some other test to verify the regression causes etc.
On an 4 core intel i5 Asus pc.
The pipe test.

1. default Bios configuration and default 3.11-rc3 kernel.

[root@localhost ~]# time ./pip1m

real 0m10.683s
user 0m0.204s
sys 0m6.597s
[root@localhost ~]# time ./pip1m

real 0m10.629s
user 0m0.185s
sys 0m6.546s
[root@localhost ~]# uname -a
Linux localhost 3.11.0-rc3 #4 SMP Wed Jul 31 16:10:56 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux

2. same as 1 and idle=halt command line parameter.
[root@localhost ~]# time ./pip1m

real 0m9.904s
user 0m0.200s
sys 0m6.209s
[root@localhost ~]# time ./pip1m

real 0m9.972s
user 0m0.201s
sys 0m6.200s

3. same as 1 and idle=nomwait command line parameter
real 0m13.634s
user 0m0.407s
sys 0m7.820s
[root@localhost ~]# time ./pip1m

real 0m13.684s
user 0m0.416s
sys 0m7.845s

4. Disable C1E C3 C6 C-states and SpeedStep in BIOS, default configuration of kernel 3.11-rc3.
[root@localhost ~]# time ./pip1m

real 0m5.371s
user 0m0.102s
sys 0m3.253s
[root@localhost ~]# time ./pip1m

real 0m5.329s
user 0m0.075s
sys 0m3.254s
[root@localhost ~]#

5. same as 4 and comment out reschedule IPI sending
[root@localhost ~]# time ./pip1m
real 0m3.883s
user 0m0.098s
sys 0m2.480s
[root@localhost ~]# time ./pip1m

real 0m3.907s
user 0m0.070s
sys 0m2.552s

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 4137890..c27f04f 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -137,7 +137,7 @@ static inline void play_dead(void)

static inline void smp_send_reschedule(int cpu)
{
- smp_ops.smp_send_reschedule(cpu);
+ /* smp_ops.smp_send_reschedule(cpu); */
}

6. same as 5 and don't reprogram clock device in remove_hrtimer.
got same result as 5.
real 0m3.915s
user 0m0.086s
sys 0m2.499s
[root@localhost ~]# time ./pip1m

real 0m3.919s
user 0m0.110s
sys 0m2.509s

So when C-states disabled, no reprogramming of hrtimer wouldn't gain better performance.
But will get more wakup chances while C-states enabled if no reprogramming clock device.

Thanks,
Ethan

在 2013-8-6，下午3:46，Mike Galbraith <bitbucket@xxxxxxxxx> 写道：

> (CCs Intel folks)
>
> On Tue, 2013-08-06 at 09:29 +0200, Mike Galbraith wrote:
>> On Tue, 2013-07-30 at 11:35 +0200, Peter Zijlstra wrote:
>>
>>> It would be good if you could do what Thomas suggested and look at which
>>> timer is actually active during your workload.
>>
>> Rebuilding regression test trees, some pipe-test results...
>>
>> I'm missing mwait_idle() rather a lot on Q6600, and at 3.8, E5620 took a
>> severe NOHZ drubbing from the menu governor.
>>
>> pipe-test, scheduling cross core
>>
>> NOTE: nohz is throttled here (patchlet below), as to not eat horrible
>> microidle cost, see E5620 v3.7.10-nothrottle below.
>>
>> Q6600
>> v3.8.13 500.6 KHz 1.000
>> v3.9.11 422.4 KHz .843
>> v3.10.4 420.2 KHz .839
>> v3.11-rc3-4-g36f571e 404.7 KHz .808
>>
>> Q6600 3.9 regression:
>> guilty party is 69fb3676 x86 idle: remove mwait_idle() and "idle=mwait" cmdline param
>> halt sucks, HTH does one activate mwait_idle_with_hints() [processor_idle()] for core2 boxen?
>>
>> E5620 +write 0 -> /dev/cpu_dma_latency, hold open
>> v3.7.10 578.5 KHz 1.000 675.4 KHz 1.000
>> v3.7.10-nothrottle 366.7 KHz .633 395.0 KHz .584
>> v3.8.13 468.3 KHz .809 690.0 KHz 1.021
>> v3.8.13 idle=mwait 595.1 KHz 1.028 NA
>> v3.9.11 462.0 KHz .798 691.1 KHz 1.023
>> v3.10.4 419.4 KHz .724 570.8 KHz .845
>> v3.11-rc3-4-g36f571e 400.1 KHz .691 538.5 KHz .797
>>
>> E5620 3.8 regression:
>> guilty party: 69a37bea cpuidle: Quickly notice prediction failure for repeat mode
>>
>>
>> Q6600 (2.4 GHz core2 quad)
>> v3.11-rc3-4-g36f571e v3.8.13
>> 7.97% [k] reschedule_interrupt 8.63% [k] __schedule
>> 6.27% [k] __schedule 6.07% [k] native_sched_clock
>> 4.74% [k] native_sched_clock 4.96% [k] system_call
>> 4.23% [k] _raw_spin_lock_irqsave 4.30% [k] _raw_spin_lock_irqsave
>> 3.39% [k] system_call 4.06% [k] resched_task
>> 2.89% [k] sched_clock_local 3.44% [k] sched_clock_local
>> 2.79% [k] mutex_lock 3.39% [k] pipe_read
>> 2.57% [k] pipe_read 3.21% [k] mutex_lock
>> 2.55% [k] __switch_to 2.98% [k] read_tsc
>> 2.24% [k] read_tsc 2.87% [k] __switch_to
>>
>>
>> E5620 (2.4 GHz Westmere quad)
>> v3.7.10 v3.7.10-nothrottle v3.7.10-nothrottle
>> 8.01% [k] __schedule 25.80% [k] _raw_spin_unlock_irqrestore 21.80% [k] _raw_spin_unlock_irqrestore
>> 4.49% [k] resched_tas 4.64% [k] __hrtimer_start_range_ns - _raw_spin_unlock_irqrestore
>> 3.94% [k] mutex_lock 4.62% [k] timerqueue_add + 37.94% __hrtimer_start_range_ns
>> 3.44% [k] __switch_to 4.54% [k] __schedule 19.69% hrtimer_cancel
>> 3.18% [k] menu_select 2.84% [k] enqueue_hrtimer tick_nohz_restart
>> 3.05% [k] copy_user_generic_string 2.64% [k] resched_task tick_nohz_idle_exit
>> 3.02% [k] task_waking_fair 2.29% [k] _raw_spin_lock_irqsave cpu_idle
>> 2.91% [k] mutex_unlock 2.28% [k] mutex_lock start_secondary
>> 2.82% [k] pipe_read 1.96% [k] __switch_to + 16.05% hrtimer_start_range_ns
>> 2.32% [k] ktime_get_real 1.73% [k] menu_select 15.46% hrtimer_start
>> tick_nohz_stop_sched_tick
>> __tick_nohz_idle_enter
>> tick_nohz_idle_enter
>> cpu_idle
>> start_secondary
>> 6.37% hrtimer_try_to_cancel
>> hrtimer_cancel
>> tick_nohz_restart
>> tick_nohz_idle_exit
>> cpu_idle
>> start_secondary
>>
>> v3.8.13 v3.8.13 idle=mwait v3.8.13 (throttled, but menu gov bites.. HARD)
>> 23.16% [k] _raw_spin_unlock_irqrestore 8.35% [k] __schedule - 22.91% [k] _raw_spin_unlock_irqrestore
>> 4.93% [k] __schedule 6.49% [k] __switch_to - _raw_spin_unlock_irqrestore
>> 3.42% [k] resched_task 5.71% [k] resched_task - 47.26% hrtimer_try_to_cancel
>> 3.27% [k] __switch_to 4.64% [k] mutex_lock hrtimer_cancel
>> 3.05% [k] mutex_lock 3.48% [k] copy_user_generic_string menu_hrtimer_cancel
>> 2.32% [k] copy_user_generic_string 3.15% [k] task_waking_fair tick_nohz_idle_exit
>> 2.30% [k] _raw_spin_lock_irqsave 3.13% [k] pipe_read cpu_idle
>> 2.15% [k] pipe_read 2.61% [k] mutex_unlock start_secondary
>> 2.15% [k] task_waking_fair 2.54% [k] finish_task_switch - 40.01% __hrtimer_start_range_ns
>> 2.08% [k] ktime_get 2.29% [k] _raw_spin_lock_irqsave hrtimer_start
>> 1.87% [k] mutex_unlock 1.91% [k] idle_cpu menu_select
>> 1.76% [k] finish_task_switch 1.84% [k] __wake_up_common cpuidle_idle_call
>> cpu_idle
>> start_secondary
>>
>> v3.9.11
>> 18.67% [k] _raw_spin_unlock_irqrestore
>> 4.36% [k] __schedule
>> 3.66% [k] __switch_to
>> 3.13% [k] mutex_lock
>> 2.97% [k] __hrtimer_start_range_ns
>> 2.69% [k] _raw_spin_lock_irqsave
>> 2.38% [k] copy_user_generic_string
>> 2.34% [k] hrtimer_reprogram.isra.32
>> 2.34% [k] task_waking_fair
>> 2.25% [k] ktime_get
>> 2.14% [k] pipe_read
>> 1.98% [k] menu_select
>>
>> v3.10.4
>> 20.42% [k] _raw_spin_unlock_irqrestore
>> 4.75% [k] __schedule
>> 4.42% [k] reschedule_interrupt <== appears in 3.10, guilty party as yet unknown
>> 3.52% [k] __switch_to
>> 3.27% [k] resched_task
>> 2.64% [k] cpuidle_enter_state
>> 2.63% [k] _raw_spin_lock_irqsave
>> 2.04% [k] copy_user_generic_string
>> 2.00% [k] cpu_idle_loop
>> 1.97% [k] mutex_lock
>> 1.90% [k] ktime_get
>> 1.75% [k] task_waking_fair
>>
>> v3.11-rc3-4-g36f571e
>> 18.96% [k] _raw_spin_unlock_irqrestore
>> 4.84% [k] __schedule
>> 4.69% [k] reschedule_interrupt
>> 3.75% [k] __switch_to
>> 2.62% [k] _raw_spin_lock_irqsave
>> 2.43% [k] cpuidle_enter_state
>> 2.28% [k] resched_task
>> 2.20% [k] cpu_idle_loop
>> 1.97% [k] copy_user_generic_string
>> 1.88% [k] ktime_get
>> 1.81% [k] task_waking_fair
>> 1.75% [k] mutex_lock
>>
>> sched: ratelimit nohz
>>
>> Entering nohz code on every micro-idle is too expensive to bear.
>>
>> Signed-off-by: Mike Galbraith <efault@xxxxxx>
>>
>> ---
>> include/linux/sched.h | 5 +++++
>> kernel/sched/core.c | 5 +++++
>> kernel/time/tick-sched.c | 2 +-
>> 3 files changed, 11 insertions(+), 1 deletion(-)
>>
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -235,9 +235,14 @@ extern int runqueue_is_locked(int cpu);
>> extern void nohz_balance_enter_idle(int cpu);
>> extern void set_cpu_sd_state_idle(void);
>> extern int get_nohz_timer_target(void);
>> +extern int sched_needs_cpu(int cpu);
>> #else
>> static inline void nohz_balance_enter_idle(int cpu) { }
>> static inline void set_cpu_sd_state_idle(void) { }
>> +static inline int sched_needs_cpu(int cpu)
>> +{
>> + return 0;
>> +}
>> #endif
>>
>> /*
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -650,6 +650,11 @@ static inline bool got_nohz_idle_kick(vo
>> return false;
>> }
>>
>> +int sched_needs_cpu(int cpu)
>> +{
>> + return cpu_rq(cpu)->avg_idle < sysctl_sched_migration_cost;
>> +}
>> +
>> #else /* CONFIG_NO_HZ_COMMON */
>>
>> static inline bool got_nohz_idle_kick(void)
>> --- a/kernel/time/tick-sched.c
>> +++ b/kernel/time/tick-sched.c
>> @@ -548,7 +548,7 @@ static ktime_t tick_nohz_stop_sched_tick
>> time_delta = timekeeping_max_deferment();
>> } while (read_seqretry(&jiffies_lock, seq));
>>
>> - if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
>> + if (sched_needs_cpu(cpu) || rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
>> arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
>> next_jiffies = last_jiffies + 1;
>> delta_jiffies = 1;
>>
>>
>
>

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Next message: boris brezillon: "Re: [PATCH] pinctrl: at91: choose appropriate handler for level interrupts"
Previous message: Aruna Balakrishnaiah: "Re: [PATCH 00/11] Add compression support to pstore"
Next in thread: Mike Galbraith: "Re: [PATCH V3]hrtimer: Fix a performance regression by disablereprogramming in remove_hrtimer"
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