linux-kernel - Re: A quick view of the performance benchmark for semaphore-like and mutex

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Date:	Tue, 17 Apr 2012 12:09:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Chen, Dennis (SRDC SW)" <Dennis1.Chen@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: A quick view of the performance benchmark for semaphore-like
 and mutex

On Tue, 2012-04-17 at 09:36 +0000, Chen, Dennis (SRDC SW) wrote:
> Just as a quick & rough test, with below changes based on mutex (almost the same as semaphore):
> 
> --- /home/dennis/Linux/linux-3.3.2-sem/kernel/mutex.c   2012-04-17 14:59:49.823177615 +0800
> +++ ./mutex.c   2012-04-17 17:00:12.963059284 +0800
> @@ -140,6 +140,7 @@ __mutex_lock_common(struct mutex *lock,
>         preempt_disable();
>         mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
>  
> +#if 0
>  #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
>         /*
>          * Optimistic spinning.
> @@ -195,6 +196,7 @@ __mutex_lock_common(struct mutex *lock,
>                 arch_mutex_cpu_relax();
>         }
>  #endif
> +#endif
>         spin_lock_mutex(&lock->wait_lock, flags);
>  
>         debug_mutex_lock_common(lock, &waiter);


or you do:

echo NO_OWNER_SPIN > /debug/sched_features


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