Re: [dpdk-users] Failing to add entry to hashmap

[Cacheco Gnudu <cacheco@posteo.net>]

On 4/8/21 10:35 PM, Cacheco Gnudu wrote:
> Hello everyone,
> 
> I'm programming a testbed with DPDK that needs to create a hashmap with
> 32768 entries and maybe more in the future. To create it, I use
> rte_hash_add_key_data() inside a for loop.
> 
> I was checking the return value of rte_hash_add_key_data() and whenever
> it was negative, the program would terminate with rte_exit(). Every time
> it added the 32224th entry it would terminate with -ENOSPC. I replaced
> rte_exit() to a simple printf() to let me know it received a negative
> value from rte_hash_add_key_data(), but would keep adding new entries
> and it does. It alternatively succeeds and fails, and when it fails its
> always with -ENOSPC. At the end only 32640 entries are added.
> 
> I pasted the hash creation code and the end of the execution output as
> well.
> 
> --- code starts here ---
> /* ... */
> #define MAX_IPS         32768
> /* ... */
> int err = 0;
> static struct rte_hash *PPVE_HASHMAP;
> struct rte_hash_parameters params = { 0 };
> params.name = "ip_filter_hashmap";
> params.entries = MAX_IPS;
> params.key_len = sizeof(uint64_t);
> params.hash_func = rte_jhash;
> params.hash_func_init_val = 0;
> params.socket_id = rte_socket_id();
> 
> uint32_t size = rte_hash_count(PPVE_HASHMAP);
> printf("%d\n", size);
> 
> PPVE_HASHMAP = rte_hash_create(&params);
> if (PPVE_HASHMAP == NULL)
>     rte_exit(EXIT_DPDK_FAIL,
>              "Failed to create hash table, errno = %d\n", rte_errno);
> size = rte_hash_count(PPVE_HASHMAP);
> printf("%d\n", size);
> 
> uint64_t key = 10, value = 0xdead;
> for (int i = 0; i < MAX_IPS; i++) {
> 
>     err = rte_hash_add_key_data(PPVE_HASHMAP, &key, &value);
>     uint32_t size = rte_hash_count(PPVE_HASHMAP);
> 
>     printf("%d\n", size);
>     if (err < 0)
>         rte_exit(EXIT_DPDK_FAIL,
>                  "Failed to add entry to hash table, err: %d\n", err);
>     key++;
> }
> /* ... */
> --- code ends here ---
> 
> 
> --- end of program output starts here ---
> 32635
> 32635
> Failed to add entry to hash table, err: -28
> 32636
> 32637
> 32638
> 32639
> 32639
> Failed to add entry to hash table, err: -28
> 32640
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> 32640
> Failed to add entry to hash table, err: -28
> --- end of program output ends here ---
> 

I was trying some workarounds and used
params.entries = MAX_IPS+1;

Apparently it worked, rte_hash_add_key_data() can add all entries now,
I'm just not sure if this approach is exactly correct. If anyone has any
suggestions let me know.

-- 
Sincerely,
Cacheco