linux-kernel - Re: [patch 1/2] add ALL_CPUS option to stop_machine

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Message-ID: <20080228221430.GA22958@Krystal>
Date:	Thu, 28 Feb 2008 17:14:30 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Max Krasnyanskiy <maxk@...lcomm.com>
Cc:	Jason Baron <jbaron@...hat.com>, akpm@...ux-foundation.org,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch 1/2] add ALL_CPUS option to stop_machine_run()

* Max Krasnyanskiy (maxk@...lcomm.com) wrote:
> Jason Baron wrote:
>> -allow stop_mahcine_run() to call a function on all cpus. Calling  
>> stop_machine_run() with a 'ALL_CPUS' invokes this new behavior.
>>  stop_machine_run() proceeds as normal until the calling cpu has
>>  invoked 'fn'. Then, we tell all the other cpus to call 'fn'.
>
> Jason, we're actually trying to reduce the usage of the stop_machine in 
> general. It's a very big hammer that kills latencies and stuff. It'd be 
> nice if we did not introduce any more dependencies on it. I guess in some 
> case there is simply no other way to handle what need to do. But please 
> think twice
> (or more :)).
>
> Max
>
>

I have a "more complex" immediate value implementation that does not
depend on such heavy lock. I made this simplified version because Rusty
preferred it, although I say from the beginning that it kills interrupt
latency. I could propose the atomic, nmi-safe version directly if enough
people are in favor of it.

Mathieu

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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