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

["ethan.zhao" <ethan.kernel@gmail.com>]

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@online.de> 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@gmx.de>
>> 
>> ---
>> 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;
>> 
>> 
> 
>