[dpdk-dev] DPDK hash function related question
Yeddula, Avinash
ayeddula at ciena.com
Mon Oct 12 19:03:16 CEST 2015
Hi Cristian,
I have configured the hash function and it compile fine with "warnings". Since librte_hash vs librte_table is 32bit vs 64bit.
librte_hash library :
/** Type of function that can be used for calculating the hash value. */
typedef uint32_t (*rte_hash_function)(const void *key, uint32_t key_len, uint32_t init_val);
librte_table library:
typedef uint64_t (*rte_table_hash_op_hash) (void *key, uint32_t key_size, uint64_t seed);
I could use one of these hash functions. This is one option, but our first priority is to use crc hash or cukoo hash.
https://github.com/scylladb/dpdk/blob/master/examples/ip_pipeline/pipeline/hash_func.h
We do not want to have those warning in our code. What do you suggest ?
Thanks
-Avinash
-----Original Message-----
From: Dumitrescu, Cristian [mailto:cristian.dumitrescu at intel.com]
Sent: Tuesday, September 22, 2015 3:05 AM
To: Yeddula, Avinash; dev at dpdk.org; Bly, Mike
Subject: RE: DPDK hash function related question
Hi Avinash,
Yes, the hash function is configurable.
Are you using a DPDK release older than 2.1? In DPDK we moved away from test_hash to CRC-based hashes. Please take a look at DPDK release 2.1 examples/ip_pipeline application: in pipeline_flow_classification_be.c, we use CRC-based hash functions defined in file hash_func.h from the same folder.
Regards,
Cristian
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Yeddula, Avinash
> Sent: Tuesday, September 22, 2015 1:34 AM
> To: dev at dpdk.org; Bly, Mike
> Subject: [dpdk-dev] DPDK hash function related question
>
> Hello All,
>
> I'm DPDK extensible bucket hash in the rte_table library of packet
> framework. My question is related to the actual hash function that
> computes the hash signature.
>
> All the available examples have initialized it to test_hash. I do not see any
> hash function available in rte_table library , that computes the
> actual signature
>
>
>
> struct rte_table_hash_ext_params hash_table_params = {
>
> .key_size = TABLE_ENTRY_KEY_SIZE,
>
> .n_keys = TABLE_MAX_SIZE,
>
> .n_buckets = TABLE_MAX_BUCKET_COUNT,
>
> .n_buckets_ext = TABLE_MAX_EXT_BUCKET_COUNT,
>
> .f_hash = test_hash,
>
> .seed = 0,
>
> .signature_offset = 0;
>
> .key_offset = __builtin_offsetof(struct metadata_t, tbl_key),
>
> };
>
>
>
> So, I wanted to use hash functions from DPDK rte_hash library. This is
> what I'm doing and looking at the code this looks ok to me.
>
> I'm at least a week or 2 away from testing this part of the code. I
> wanted to confirm that, there is no fundamental flaw in using the DPDK
> rte_hash library and rte_table library like this. Could someone confirm this please ?
>
>
>
> #define DEFAULT_HASH_FUNC rte_hash_crc
>
>
>
> struct rte_table_hash_ext_params hash_table_params = {
>
> .key_size = TABLE_ENTRY_KEY_SIZE,
>
> .n_keys = TABLE_MAX_SIZE,
>
> .n_buckets = TABLE_MAX_BUCKET_COUNT,
>
> .n_buckets_ext = TABLE_MAX_EXT_BUCKET_COUNT,
>
> .f_hash = DEFAULT_HASH_FUNC ,
>
> .seed = 0,
>
> .signature_offset = 0;
>
> .key_offset = __builtin_offsetof(struct metadata_t, tbl_key),
>
> };
>
>
>
> Thanks
>
> -Avinash
>
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