[DTrace-devel] [PATCH v3 03/11] htab: add dt_htab_entries

[Kris Van Hees]

Since you introduce a total number of entries for a hash, perhaps also change
the dt_htab_stats() function since it no longer has to calculate that count
anymore

On Mon, Nov 01, 2021 at 02:29:39PM +0000, Nick Alcock wrote:
> This returns the number of entries added to the hashtable.
> 
> We also fix a bug in the per-bucket entry count (used only by
> dt_htab_stats): it was being incremented on addition but never
> decremented on removal, even though dt_htab_ops.del had better be an
> inverse of dt_htab_ops.add, and nentries was being incremented on
> addition -- and we don't have tombstones in the bucket chain list, so
> the number of nentries in a bucket really does fall on removal.
> 
> Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
> ---
>  libdtrace/dt_htab.c | 13 +++++++++++++
>  libdtrace/dt_htab.h |  1 +
>  2 files changed, 14 insertions(+)
> 
> diff --git a/libdtrace/dt_htab.c b/libdtrace/dt_htab.c
> index 65296749bf74..e4876fc93042 100644
> --- a/libdtrace/dt_htab.c
> +++ b/libdtrace/dt_htab.c
> @@ -43,6 +43,7 @@ struct dt_htab {
>  	int		size;
>  	int		mask;
>  	int		nbuckets;
> +	size_t		nentries;
>  	dt_htab_ops_t	*ops;
>  };
>  
> @@ -59,6 +60,7 @@ dt_htab_t *dt_htab_create(dtrace_hdl_t *dtp, dt_htab_ops_t *ops)
>  	htab->size = 1;
>  	htab->mask = htab->size - 1;
>  	htab->nbuckets = 0;
> +	htab->nentries = 0;
>  	htab->ops = ops;
>  
>  	htab->tab = dt_calloc(dtp, htab->size, sizeof(dt_hbucket_t *));
> @@ -158,6 +160,7 @@ retry:
>  add:
>  	bucket->head = htab->ops->add(bucket->head, entry);
>  	bucket->nentries++;
> +	htab->nentries++;
>  
>  	return 0;
>  }
> @@ -199,6 +202,8 @@ int dt_htab_delete(dt_htab_t *htab, void *entry)
>  		return -ENOENT;
>  
>  	head = htab->ops->del(bucket->head, entry);
> +	bucket->nentries--;
> +	htab->nentries--;
>  	if (!head) {
>  		dt_hbucket_t	*b = htab->tab[idx];
>  
> @@ -219,6 +224,14 @@ int dt_htab_delete(dt_htab_t *htab, void *entry)
>  	return 0;
>  }
>  
> +/*
> + * Return the number of entries in the hashtable.
> + */
> +size_t dt_htab_entries(const dt_htab_t *htab)
> +{
> +	return htab->nentries;
> +}
> +
>  /*
>   * Report statistics on the given hashtable.
>   */
> diff --git a/libdtrace/dt_htab.h b/libdtrace/dt_htab.h
> index 3a716357362f..e12c96fc9006 100644
> --- a/libdtrace/dt_htab.h
> +++ b/libdtrace/dt_htab.h
> @@ -88,6 +88,7 @@ extern dt_htab_t *dt_htab_create(struct dtrace_hdl *dtp, dt_htab_ops_t *ops);
>  extern void dt_htab_destroy(struct dtrace_hdl *dtp, dt_htab_t *htab);
>  extern int dt_htab_insert(dt_htab_t *htab, void *entry);
>  extern void *dt_htab_lookup(const dt_htab_t *htab, const void *entry);
> +extern size_t dt_htab_entries(const dt_htab_t *htab);
>  extern int dt_htab_delete(dt_htab_t *htab, void *entry);
>  extern void dt_htab_stats(const char *name, const dt_htab_t *htab);
>  
> -- 
> 2.33.1.257.g9e0974a4e8
> 
> 
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