linux-kernel - Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall

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Date:	Fri, 24 Nov 2006 21:04:19 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	"Paul E. McKenney" <paulmck@...ibm.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync

On Fri, Nov 24 2006, Oleg Nesterov wrote:
> Ok, synchronize_xxx() passed 1 hour rcutorture test on dual P-III.
> 
> It behaves the same as srcu but optimized for writers. The fast path
> for synchronize_xxx() is mutex_lock() + atomic_read() + mutex_unlock().
> The slow path is __wait_event(), no polling. However, the reader does
> atomic inc/dec on lock/unlock, and the counters are not per-cpu.
> 
> Jens, is it ok for you? Alan, Paul, what is your opinion?

This looks good from my end, much more appropriate than the current SRCU
code. Even if I could avoid synchronize_srcu() for most cases, when I
did have to issue it, the 3x synchronize_sched() was a performance
killer.

Thanks Oleg! And Alan and Paul for your excellent ideas.

-- 
Jens Axboe

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