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SubjectRe: [RFC] sched: Limit idle_balance() when it is being used too frequently
On Thu, Jul 18, 2013 at 12:06:39PM -0700, Jason Low wrote:

> N = 1
> -----
> 19.21% reaim [k] __read_lock_failed
> 14.79% reaim [k] mspin_lock
> 12.19% reaim [k] __write_lock_failed
> 7.87% reaim [k] _raw_spin_lock
> 2.03% reaim [k] start_this_handle
> 1.98% reaim [k] update_sd_lb_stats
> 1.92% reaim [k] mutex_spin_on_owner
> 1.86% reaim [k] update_cfs_rq_blocked_load
> 1.14% swapper [k] intel_idle
> 1.10% reaim [.] add_long
> 1.09% reaim [.] add_int
> 1.08% reaim [k] load_balance

But but but but.. wth is causing this? The only thing we do more of with
N=1 is idle_balance(); where would that cause __{read,write}_lock_failed
and or mspin_lock() contention like that.

There shouldn't be a rwlock_t in the entire scheduler; those things suck
worse than quicksand.

If, as Rik thought, we'd have more rq->lock contention, then I'd
expected _raw_spin_lock to be up highest.


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