linux-kernel - Re: [PATCH] sunrpc: make the cache cleaner workqueue deferrable

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Date:	Tue, 6 Jul 2010 12:28:16 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Artem Bityutskiy <dedekind1@...il.com>
Cc:	Neil Brown <neilb@...e.de>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sunrpc: make the cache cleaner workqueue deferrable

On Thu, Jul 01, 2010 at 06:05:56PM +0300, Artem Bityutskiy wrote:
> From: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
> 
> This patch makes the cache_cleaner workqueue deferrable, to prevent
> unnecessary system wake-ups, which is very important for embedded
> battery-powered devices.
> 
> do_cache_clean() is called every 30 seconds at the moment, and often
> makes the system wake up from its power-save sleep state. With this
> change, when the workqueue uses a deferrable timer, the
> do_cache_clean() invocation will be delayed and combined with the
> closest "real" wake-up. This improves the power consumption situation.
> 
> Note, I tried to create a DECLARE_DELAYED_WORK_DEFERRABLE() helper
> macro, similar to DECLARE_DELAYED_WORK(), but failed because of the
> way the timer wheel core stores the deferrable flag (it is the
> LSBit in the time->base pointer). My attempt to define a static
> variable with this bit set ended up with the "initializer element is
> not constant" error.
> 
> Thus, I have to use run-time initialization, so I created a new
> cache_initialize() function which is called once when sunrpc is
> being initialized.

Thanks, applying for 2.6.36.

--b.

> 
> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
> ---
>  include/linux/sunrpc/cache.h |    1 +
>  net/sunrpc/cache.c           |    7 ++++++-
>  net/sunrpc/sunrpc_syms.c     |    1 +
>  3 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
> index 6f52b4d..7bf3e84 100644
> --- a/include/linux/sunrpc/cache.h
> +++ b/include/linux/sunrpc/cache.h
> @@ -192,6 +192,7 @@ extern int cache_check(struct cache_detail *detail,
>  extern void cache_flush(void);
>  extern void cache_purge(struct cache_detail *detail);
>  #define NEVER (0x7FFFFFFF)
> +extern void __init cache_initialize(void);
>  extern int cache_register(struct cache_detail *cd);
>  extern void cache_unregister(struct cache_detail *cd);
>  
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 58de76c..939d048 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -320,7 +320,7 @@ static struct cache_detail *current_detail;
>  static int current_index;
>  
>  static void do_cache_clean(struct work_struct *work);
> -static DECLARE_DELAYED_WORK(cache_cleaner, do_cache_clean);
> +static struct delayed_work cache_cleaner;
>  
>  static void sunrpc_init_cache_detail(struct cache_detail *cd)
>  {
> @@ -1504,6 +1504,11 @@ static int create_cache_proc_entries(struct cache_detail *cd)
>  }
>  #endif
>  
> +void __init cache_initialize(void)
> +{
> +	INIT_DELAYED_WORK_DEFERRABLE(&cache_cleaner, do_cache_clean);
> +}
> +
>  int cache_register(struct cache_detail *cd)
>  {
>  	int ret;
> diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
> index f438347..c52b184 100644
> --- a/net/sunrpc/sunrpc_syms.c
> +++ b/net/sunrpc/sunrpc_syms.c
> @@ -43,6 +43,7 @@ init_sunrpc(void)
>  #ifdef CONFIG_PROC_FS
>  	rpc_proc_init();
>  #endif
> +	cache_initialize();
>  	cache_register(&ip_map_cache);
>  	cache_register(&unix_gid_cache);
>  	svc_init_xprt_sock();	/* svc sock transport */
> -- 
> 1.7.0.1
> 
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