Re: [PATCH v7 1/4] spinlock: A new lockref structure for locklessupdate of refcount

[Waiman Long]

On 09/04/2013 05:34 PM, Linus Torvalds wrote:
> On Wed, Sep 4, 2013 at 12:25 PM, Waiman Long<waiman.long@xxxxxx>  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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