On Sat, Apr 27, 2013 at 03:18:59AM +0400, Glauber Costa wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/dcache.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index e689268..8df1cd9 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;
> +}
> +
I was going to raise questions on the use of for_each_possible_cpu() and
ask why it was not for_each_online_cpu() but I see now that it has been
discussed already -- it's to avoid lost counters from offlined CPUs
without having to cope with CPU hotplug just to keep a proc handler
happy.
A comment either here or in the changelog saying that
for_each_possible_cpu() is deliberate would not hurt in case someone
tries to "fix" this but it's no big deal so
Acked-by: Mel Gorman <mgorman@xxxxxxx>
--
Mel Gorman
SUSE Labs
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