Re: [PATCH] nfsd: remove recurring workqueue job to clean DRC

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Nov 04, 2015 at 11:02:29AM -0500, Jeff Layton wrote:
> We have a shrinker, we clean out the cache when nfsd is shut down, and
> prune the chains on each request. A recurring workqueue job seems like
> unnecessary overhead. Just remove it.

Thanks, applying.--b.

> 
> Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> ---
>  fs/nfsd/nfscache.c | 26 --------------------------
>  1 file changed, 26 deletions(-)
> 
> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index 46ec934f5dee..8af64b6ffe91 100644
> --- a/fs/nfsd/nfscache.c
> +++ b/fs/nfsd/nfscache.c
> @@ -63,7 +63,6 @@ static unsigned int		longest_chain;
>  static unsigned int		longest_chain_cachesize;
>  
>  static int	nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
> -static void	cache_cleaner_func(struct work_struct *unused);
>  static unsigned long nfsd_reply_cache_count(struct shrinker *shrink,
>  					    struct shrink_control *sc);
>  static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink,
> @@ -76,13 +75,6 @@ static struct shrinker nfsd_reply_cache_shrinker = {
>  };
>  
>  /*
> - * locking for the reply cache:
> - * A cache entry is "single use" if c_state == RC_INPROG
> - * Otherwise, it when accessing _prev or _next, the lock must be held.
> - */
> -static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);
> -
> -/*
>   * Put a cap on the size of the DRC based on the amount of available
>   * low memory in the machine.
>   *
> @@ -203,7 +195,6 @@ void nfsd_reply_cache_shutdown(void)
>  	unsigned int i;
>  
>  	unregister_shrinker(&nfsd_reply_cache_shrinker);
> -	cancel_delayed_work_sync(&cache_cleaner);
>  
>  	for (i = 0; i < drc_hashsize; i++) {
>  		struct list_head *head = &drc_hashtbl[i].lru_head;
> @@ -232,7 +223,6 @@ lru_put_end(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
>  {
>  	rp->c_timestamp = jiffies;
>  	list_move_tail(&rp->c_lru, &b->lru_head);
> -	schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
>  }
>  
>  static long
> @@ -266,7 +256,6 @@ prune_cache_entries(void)
>  {
>  	unsigned int i;
>  	long freed = 0;
> -	bool cancel = true;
>  
>  	for (i = 0; i < drc_hashsize; i++) {
>  		struct nfsd_drc_bucket *b = &drc_hashtbl[i];
> @@ -275,26 +264,11 @@ prune_cache_entries(void)
>  			continue;
>  		spin_lock(&b->cache_lock);
>  		freed += prune_bucket(b);
> -		if (!list_empty(&b->lru_head))
> -			cancel = false;
>  		spin_unlock(&b->cache_lock);
>  	}
> -
> -	/*
> -	 * Conditionally rearm the job to run in RC_EXPIRE since we just
> -	 * ran the pruner.
> -	 */
> -	if (!cancel)
> -		mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
>  	return freed;
>  }
>  
> -static void
> -cache_cleaner_func(struct work_struct *unused)
> -{
> -	prune_cache_entries();
> -}
> -
>  static unsigned long
>  nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
>  {
> -- 
> 2.4.3