Re: [PATCH v2 03/13] tools/xenstore: modify interface of create_hashtable()

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 30/03/2023 09:50, Juergen Gross wrote:
> The minsize parameter of create_hashtable() doesn't have any real use
> case for Xenstore, so drop it.
>
> For better talloc_report_full() diagnostic output add a name parameter
> to create_hashtable().
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>   tools/xenstore/hashtable.c        | 20 ++++++--------------
>   tools/xenstore/hashtable.h        |  4 ++--
>   tools/xenstore/xenstored_core.c   |  2 +-
>   tools/xenstore/xenstored_domain.c |  4 ++--
>   4 files changed, 11 insertions(+), 19 deletions(-)
>
> diff --git a/tools/xenstore/hashtable.c b/tools/xenstore/hashtable.c
> index c1b11743bb..ab1e687d0b 100644
> --- a/tools/xenstore/hashtable.c
> +++ b/tools/xenstore/hashtable.c
> @@ -55,36 +55,28 @@ static unsigned int loadlimit(unsigned int pindex)
>       return ((uint64_t)primes[pindex] * MAX_LOAD_PERCENT) / 100;
>   }
>   
> -struct hashtable *create_hashtable(const void *ctx, unsigned int minsize,
> +struct hashtable *create_hashtable(const void *ctx, const char *name,
>                                      unsigned int (*hashf) (const void *),
>                                      int (*eqf) (const void *, const void *),
>                                      unsigned int flags)
>   {
>       struct hashtable *h;
> -    unsigned int pindex, size = primes[0];
> -
> -    /* Check requested hashtable isn't too large */
> -    if (minsize > (1u << 30)) return NULL;
> -
> -    /* Enforce size as prime */
> -    for (pindex=0; pindex < PRIME_TABLE_LEN; pindex++) {
> -        if (primes[pindex] > minsize) { size = primes[pindex]; break; }
> -    }
>   
>       h = talloc_zero(ctx, struct hashtable);
>       if (NULL == h)
>           goto err0;
> -    h->table = talloc_zero_array(h, struct entry *, size);
> +    talloc_set_name_const(h, name);
> +    h->table = talloc_zero_array(h, struct entry *, primes[0]);
>       if (NULL == h->table)
>           goto err1;
>   
> -    h->tablelength  = size;
> +    h->tablelength  = primes[0];
I find the connection between this line, ...

>       h->flags        = flags;
> -    h->primeindex   = pindex;
> +    h->primeindex   = 0;
... this one and ...

>       h->entrycount   = 0;
>       h->hashfn       = hashf;
>       h->eqfn         = eqf;
> -    h->loadlimit    = loadlimit(pindex);
> +    h->loadlimit    = loadlimit(0);
... now more difficult to find. How about setting h->primeindex first 
and then using it in place of 0?
>       return h;
>   
>   err1:
> diff --git a/tools/xenstore/hashtable.h b/tools/xenstore/hashtable.h
> index 04310783b6..0e1a6f61c2 100644
> --- a/tools/xenstore/hashtable.h
> +++ b/tools/xenstore/hashtable.h
> @@ -10,7 +10,7 @@ struct hashtable;
>      
>    * @name                    create_hashtable
>    * @param   ctx             talloc context to use for allocations
> - * @param   minsize         minimum initial size of hashtable
> + * @param   name            talloc name of the hashtable
>    * @param   hashfunction    function for hashing keys
>    * @param   key_eq_fn       function for determining key equality
>    * @param   flags           flags HASHTABLE_*
> @@ -23,7 +23,7 @@ struct hashtable;
>   #define HASHTABLE_FREE_KEY   (1U << 1)
>   
>   struct hashtable *
> -create_hashtable(const void *ctx, unsigned int minsize,
> +create_hashtable(const void *ctx, const char *name,
>                    unsigned int (*hashfunction) (const void *),
>                    int (*key_eq_fn) (const void *, const void *),
>                    unsigned int flags
> diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
> index 7214b3df03..6ce7be3161 100644
> --- a/tools/xenstore/xenstored_core.c
> +++ b/tools/xenstore/xenstored_core.c
> @@ -2511,7 +2511,7 @@ void check_store(void)
>         struct check_store_data data;
>   
>   	/* Don't free values (they are all void *1) */
> -       data.reachable = create_hashtable(NULL, 16, hash_from_key_fn,
> +       data.reachable = create_hashtable(NULL, "checkstore", hash_from_key_fn,
>                                           keys_equal_fn, HASHTABLE_FREE_KEY);
>         if (!data.reachable) {
>                 log("check_store: ENOMEM");
> diff --git a/tools/xenstore/xenstored_domain.c 
> b/tools/xenstore/xenstored_domain.c
> index df64c87efc..6d40aefc63 100644
> --- a/tools/xenstore/xenstored_domain.c
> +++ b/tools/xenstore/xenstored_domain.c
> @@ -1017,7 +1017,7 @@ void domain_init(int evtfd)
>         int rc;
>   
>   	/* Start with a random rather low domain count for the hashtable. */
> -       domhash = create_hashtable(NULL, 8, domhash_fn, domeq_fn, 0);
> +       domhash = create_hashtable(NULL, "domains", domhash_fn, domeq_fn, 0);
>         if (!domhash)
>                 barf_perror("Failed to allocate domain hashtable");
>   
> @@ -1804,7 +1804,7 @@ struct hashtable *domain_check_acc_init(void)
>   {
>         struct hashtable *domains;
>   
> -	domains = create_hashtable(NULL, 8, domhash_fn, domeq_fn,
> +       domains = create_hashtable(NULL, "domain_check", domhash_fn, domeq_fn,
>                                    HASHTABLE_FREE_VALUE);
>         if (!domains)
>                 return NULL;
Cheers,

--
Julien Grall