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SubjectRe: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount
On 09/04/2013 05:34 PM, Linus Torvalds wrote:
> On Wed, Sep 4, 2013 at 12:25 PM, Waiman Long<waiman.long@hp.com> wrote:
>> Yes, the perf profile was taking from an 80-core machine. There isn't any
>> scalability issue hiding for the short workload on an 80-core machine.
>>
>> However, I am certain that more may pop up when running in an even larger
>> machine like the prototype 240-core machine that our team has been testing
>> on.
> Sure. Please let us know, I think it's going to be interesting to see
> what that shows.
>
> SGI certainly did much larger machines, but their primary target
> tended to be all user space, so they had things like "tons of
> concurrent page faults in the same process" rather than filename
> lookup or the tty layer.
>
> Linus

I think SGI is more focus on compute-intensive workload. HP is more
focus on high-end commercial workload like SAP HANA. Below was a sample
perf profile of the high-systime workload on a 240-core prototype
machine (HT off) with 3.10-rc1 kernel with my lockref and seqlock patches:

9.61% 3382925 swapper [kernel.kallsyms] [k]
_raw_spin_lock
|--59.90%-- rcu_process_callbacks
|--19.41%-- load_balance
|--9.58%-- rcu_accelerate_cbs
|--6.70%-- tick_do_update_jiffies64
|--1.46%-- scheduler_tick
|--1.17%-- sched_rt_period_timer
|--0.56%-- perf_adjust_freq_unthr_context
--1.21%-- [...]

6.34% 99 reaim [kernel.kallsyms] [k]
_raw_spin_lock
|--73.96%-- load_balance
|--11.98%-- rcu_process_callbacks
|--2.21%-- __mutex_lock_slowpath
|--2.02%-- rcu_accelerate_cbs
|--1.95%-- wake_up_new_task
|--1.70%-- scheduler_tick
|--1.67%-- xfs_alloc_log_agf
|--1.24%-- task_rq_lock
|--1.15%-- try_to_wake_up
--2.12%-- [...]

5.39% 2 reaim [kernel.kallsyms] [k]
_raw_spin_lock_irqsave
|--95.08%-- rwsem_wake
|--1.80%-- rcu_process_callbacks
|--1.03%-- prepare_to_wait
|--0.59%-- __wake_up
--1.50%-- [...]

2.28% 1 reaim [kernel.kallsyms] [k]
_raw_spin_lock_irq
|--90.56%-- rwsem_down_write_failed
|--9.25%-- __schedule
--0.19%-- [...]

Longman


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