linux-kernel - Re: [RFC PATCH 0/5] Add kernel-offset file and make rcu_read

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Message-ID: <20110328221755.GQ2287@linux.vnet.ibm.com>
Date:	Mon, 28 Mar 2011 15:17:55 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Jan Beulich <jbeulich@...ell.com>,
	David Howells <dhowells@...hat.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Serge Hallyn <serue@...ibm.com>, linux-kernel@...r.kernel.org,
	Christoph Lameter <clameter@....com>,
	Sam Ravnborg <sam@...nborg.org>
Subject: Re: [RFC PATCH 0/5] Add kernel-offset file and make
 rcu_read_[un]lock() included

On Mon, Mar 28, 2011 at 10:55:41AM +0800, Lai Jiangshan wrote:
> 
> 
> __rcu_read_[un]lock() are so simple functions and called so
> frequent, it is not good that a function call overhead is
> required when use them. It would be better if we declare
> them inline and let the compiler do the choice.
> 
> We add kernel-offset.c for TASK_RCU_OFFSET, which enable we declare
> rcu_read_[un]lock() as inline function.
> 
> Adding kernel-offset.c does not have any effect for the result
> compiled kernel, it just adds a small and fast step in the kbuid stage.

Good stuff, thank you!  It will be really cool to have inlined
rcu_read_lock() and rcu_read_unlock() for TREE_PREEMPT_RCU!

I will queue this up in a few days, currently chasing down a problem
located in the upcoming TREE_RCU softirq-to-kthread commit.

							Thanx, Paul

> Lai Jiangshan (5):
>   task_rcu_struct
>   kbuild_dedumplicated
>   add_kernel_offset
>   access task's task_rcu_struct without include sched.h
>   rcu inline
> 
>  Kbuild                    |   99 ++++++++++++++++---------------
>  include/linux/init_task.h |   25 +--------
>  include/linux/rcupdate.h  |  144 ++++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/sched.h     |   39 +------------
>  kernel/kernel-offsets.c   |   17 +++++
>  kernel/rcutiny_plugin.h   |   58 ++++--------------
>  kernel/rcutree_plugin.h   |   69 ++++++----------------
>  7 files changed, 243 insertions(+), 208 deletions(-)
>  create mode 100644 kernel/kernel-offsets.c
> 
> -- 
> 1.7.4
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