Re: [PATCH] better align percpu counter (Was Re: [tip:sched/core]sched: cpuacct: Use bigger percpu counter batch values for stats counters

[KAMEZAWA Hiroyuki]

On Thu, 20 Aug 2009 17:41:23 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:

>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
>  include/linux/percpu_counter.h |   12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.31-rc6/include/linux/percpu_counter.h
> ===================================================================
> --- linux-2.6.31-rc6.orig/include/linux/percpu_counter.h	2009-08-20 12:09:27.000000000 +0900
> +++ linux-2.6.31-rc6/include/linux/percpu_counter.h	2009-08-20 17:31:13.000000000 +0900
> @@ -14,14 +14,24 @@
>  #include <linux/types.h>
>  
>  #ifdef CONFIG_SMP
> +struct __percpu_counter_padding {
> +	char x[0];
> +} ____cacheline_internodealigned_in_smp;

above alignement is too big...plz ignore this patch :(

-Kame


> +#define CACHELINE_PADDING(name)  struct __percpu_counter_padding name
>  
>  struct percpu_counter {
> +	/*
> +	 * This pointer is persistent and accessed firstly.
> +	 * Then, should not be purged by locking in other cpus.
> +	 */
> +	s32 *counters;
> +	CACHELINE_PADDING(pad);
>  	spinlock_t lock;
>  	s64 count;
>  #ifdef CONFIG_HOTPLUG_CPU
> +	/* rarely accessed field */
>  	struct list_head list;	/* All percpu_counters are on a list */
>  #endif
> -	s32 *counters;
>  };
>  
>  extern int percpu_counter_batch;
> 
> 
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