linux-kernel - Re: [PATCH v3] rcu: Deinline rcu_read_lock_sched_held() if DEBUG_LOCK

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Date:	Tue, 26 May 2015 12:04:46 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rcu: Deinline rcu_read_lock_sched_held() if
 DEBUG_LOCK_ALLOC

On Tue, 26 May 2015 17:48:34 +0200
Denys Vlasenko <dvlasenk@...hat.com> wrote:

> DEBUG_LOCK_ALLOC=y is not a production setting, but it is
> not very unusual either. Many developers routinely
> use kernels built with it enabled.
> 
> Apart from being selected by hand, it is also auto-selected by
> PROVE_LOCKING "Lock debugging: prove locking correctness" and
> LOCK_STAT "Lock usage statistics" config options.
> LOCK STAT is necessary for "perf lock" to work.
> 
> I wouldn't spend too much time optimizing it, but this particular
> function has a very large cost in code size: when it is deinlined,
> code size decreases by 830,000 bytes:
> 
>     text     data      bss       dec     hex filename
> 85674192 22294776 20627456 128596424 7aa39c8 vmlinux.before
> 84837612 22294424 20627456 127759492 79d7484 vmlinux
> 
> (with this config: http://busybox.net/~vda/kernel_config)
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> CC: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> CC: Josh Triplett <josh@...htriplett.org>
> CC: Steven Rostedt <rostedt@...dmis.org>
> CC: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> CC: Lai Jiangshan <laijs@...fujitsu.com>
> CC: Tejun Heo <tj@...nel.org>
> CC: Oleg Nesterov <oleg@...hat.com>
> CC: linux-kernel@...r.kernel.org

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve
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