linux-kernel - Re: [PATCH 2/3] workqueues: microoptimize set_wq

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Message-ID: <4B85EA24.5020409@kernel.org>
Date:	Thu, 25 Feb 2010 12:10:28 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Samu Onkalo <samu.p.onkalo@...ia.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] workqueues: microoptimize set_wq_data()

On 02/25/2010 05:20 AM, Oleg Nesterov wrote:
> The comment correctly states that the _PENDING bit must be set and
> we even have the BUG_ON() check. But this means there is no need to
> set WORK_STRUCT_PENDING explicitely and load work_data_bits() twice,
> we can rely on WORK_STRUCT_FLAG_MASK which contains _PENDING.
> 
> Shaves 32 bytes from workqueue.o.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
> 
>  kernel/workqueue.c |    7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> --- wq/kernel/workqueue.c~2_CLEANUP_SET_DATA	2010-02-24 20:55:53.000000000 +0100
> +++ wq/kernel/workqueue.c	2010-02-24 20:58:37.000000000 +0100
> @@ -220,12 +220,9 @@ struct cpu_workqueue_struct *wq_per_cpu(
>  static inline void set_wq_data(struct work_struct *work,
>  				struct cpu_workqueue_struct *cwq)
>  {
> -	unsigned long new;
> -
> -	BUG_ON(!work_pending(work));
> -
> -	new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
> +	unsigned long new = (unsigned long)cwq;
>  	new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
> +	BUG_ON(!(new & (1UL << WORK_STRUCT_PENDING)));
>  	atomic_long_set(&work->data, new);

Will apply under cmwq patches for the next merge window.

Thanks.

-- 
tejun
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