[PATCH v2 03/28] dcache: convert dentry_stat.nr_unused to per-cpu counters

Greg Thelen gthelen at google.com
Fri Apr 5 01:09:31 UTC 2013


On Fri, Mar 29 2013, Glauber Costa wrote:

> From: Dave Chinner <dchinner at redhat.com>
>
> Before we split up the dcache_lru_lock, the unused dentry counter
> needs to be made independent of the global dcache_lru_lock. Convert
> it to per-cpu counters to do this.
>
> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> Reviewed-by: Christoph Hellwig <hch at lst.de>
> ---
>  fs/dcache.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index fbfae008..f1196f2 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -118,6 +118,7 @@ struct dentry_stat_t dentry_stat = {
>  };
>  
>  static DEFINE_PER_CPU(unsigned int, nr_dentry);
> +static DEFINE_PER_CPU(unsigned int, nr_dentry_unused);
>  
>  #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
>  static int get_nr_dentry(void)
> @@ -129,10 +130,20 @@ static int get_nr_dentry(void)
>  	return sum < 0 ? 0 : sum;
>  }
>  
> +static int get_nr_dentry_unused(void)
> +{
> +	int i;
> +	int sum = 0;
> +	for_each_possible_cpu(i)
> +		sum += per_cpu(nr_dentry_unused, i);
> +	return sum < 0 ? 0 : sum;
> +}

Just checking...  If cpu x is removed, then its per cpu nr_dentry_unused
count survives so we don't leak nr_dentry_unused.  Right?  I see code in
percpu_counter_sum_positive() to explicitly handle this case and I want
to make sure we don't need it here.

[snip]


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