Re: [PATCH 5/6] libdiskfs: remove the statistics code from the name cache

[Samuel Thibault]

Justus Winter, le Thu 29 May 2014 18:41:03 +0200, a écrit :
> The current name cache lookup operation completes in O(n) time.  This
> means that making the cache too large would decrease the performance.
> Therefore it was required to tune the size, hence the need for
> statistics.
> 
> We will use a data structure with worst case constant lookup times in
> the future, removing the need to fine tune the cache size.

Ack.

> * libdiskfs/name-cache.c: Remove the statistics code from the name
> cache.
> ---
>  libdiskfs/name-cache.c | 66 
> +-------------------------------------------------
>  1 file changed, 1 insertion(+), 65 deletions(-)
> 
> diff --git a/libdiskfs/name-cache.c b/libdiskfs/name-cache.c
> index a212a6d..25b5d0d 100644
> --- a/libdiskfs/name-cache.c
> +++ b/libdiskfs/name-cache.c
> @@ -45,29 +45,12 @@ struct lookup_cache
>  
>    /* Strlen of NAME.  If this is zero, it's an unused entry. */
>    size_t name_len;
> -
> -  /* XXX */
> -  int stati;
>  };
>  
>  /* The contents of the cache in no particular order */
>  static struct cacheq lookup_cache = { sizeof (struct lookup_cache) };
>  
>  static pthread_spinlock_t cache_lock = PTHREAD_SPINLOCK_INITIALIZER;
> -
> -/* Buffer to hold statistics */
> -static struct stats
> -{
> -  long pos_hits;
> -  long neg_hits;
> -  long miss;
> -  long fetch_errors;
> -} statistics;
> -
> -#define PARTIAL_THRESH 100
> -#define NPARTIALS MAXCACHE / PARTIAL_THRESH
> -struct stats partial_stats [NPARTIALS];
> -
>  
>  /* If there's an entry for NAME, of length NAME_LEN, in directory DIR in the
>     cache, return its entry, otherwise 0.  CACHE_LOCK must be held.  */
> @@ -85,10 +68,7 @@ find_cache (struct node *dir, const char *name, size_t 
> name_len)
>      if (c->name_len == name_len
>       && c->dir_cache_id == dir->cache_id
>       && c->name[0] == name[0] && strcmp (c->name, name) == 0)
> -      {
> -     c->stati = i / 100;
> -     return c;
> -      }
> +      return c;
>  
>    return 0;
>  }
> @@ -152,46 +132,6 @@ diskfs_purge_lookup_cache (struct node *dp, struct node 
> *np)
>    pthread_spin_unlock (&cache_lock);
>  }
>  
> -/* Register a negative hit for an entry in the Nth stat class */
> -void
> -register_neg_hit (int n)
> -{
> -  int i;
> -
> -  statistics.neg_hits++;
> -
> -  for (i = 0; i < n; i++)
> -    partial_stats[i].miss++;
> -  for (; i < NPARTIALS; i++)
> -    partial_stats[i].neg_hits++;
> -}
> -
> -/* Register a positive hit for an entry in the Nth stat class */
> -void
> -register_pos_hit (int n)
> -{
> -  int i;
> -
> -  statistics.pos_hits++;
> -
> -  for (i = 0; i < n; i++)
> -    partial_stats[i].miss++;
> -  for (; i < NPARTIALS; i++)
> -    partial_stats[i].pos_hits++;
> -}
> -
> -/* Register a miss */
> -void
> -register_miss ()
> -{
> -  int i;
> -
> -  statistics.miss++;
> -  for (i = 0; i < NPARTIALS; i++)
> -    partial_stats[i].miss++;
> -}
> -
> -
>  
>  /* Scan the cache looking for NAME inside DIR.  If we don't know
>     anything entry at all, then return 0.  If the entry is confirmed to
> @@ -214,14 +154,12 @@ diskfs_check_lookup_cache (struct node *dir, const char 
> *name)
>        if (id == 0)
>       /* A negative cache entry.  */
>       {
> -       register_neg_hit (c->stati);
>         pthread_spin_unlock (&cache_lock);
>         return (struct node *)-1;
>       }
>        else if (id == dir->cache_id)
>       /* The cached node is the same as DIR.  */
>       {
> -       register_pos_hit (c->stati);
>         pthread_spin_unlock (&cache_lock);
>         diskfs_nref (dir);
>         return dir;
> @@ -232,7 +170,6 @@ diskfs_check_lookup_cache (struct node *dir, const char 
> *name)
>         struct node *np;
>         error_t err;
>  
> -       register_pos_hit (c->stati);
>         pthread_spin_unlock (&cache_lock);
>  
>         if (name[0] == '.' && name[1] == '.' && name[2] == '\0')
> @@ -259,7 +196,6 @@ diskfs_check_lookup_cache (struct node *dir, const char 
> *name)
>       }
>      }
>  
> -  register_miss ();
>    pthread_spin_unlock (&cache_lock);
>  
>    return 0;
> -- 
> 2.0.0.rc2
> 

-- 
Samuel
 Profitant de cette occasion, vous serait-il possible de rebooter 
 aussi Modérator et son petit copain qui gère les ressources de 
 download ?
 -+- OB in NPC : Apprendre à flasher son personnel -+-