Re: [PATCH v6] hash: add XOR32 hash function

[Bili Dong <qobilidop@gmail.com>]

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Thanks Vladimir for your suggestion! Indeed your version looks cleaner.

I will make the changes (including the new test case you mentioned) and
prepare a new version this weekend.

Regards,
Bili

On Thu, Jun 15, 2023 at 10:15 AM Vladimir Medvedkin <medvedkinv@gmail.com>
wrote:

> Hi Bili,
>
> The rte_hash_xor32() implementation looks a bit messy with respect to byte
> ordering, i.e. in case when data_len >= 8 init_val is byte swapped, but in
> other cases the data is byte swapped.
> Maybe it could be implemented like:
>
> static inline uint32_t
> rte_hash_xor32(const void *data, uint32_t data_len, uint32_t init_val)
> {
>         const uint8_t *data8 = data;
>         uint64_t hash64 = 0;
>         uint32_t hash32;
>         unsigned int i;
>
>         for (i = 0; i < data_len / 8; i++) {
>                 hash64 ^= *(const uint64_t *)data8;
>                 data8 += 8;
>         }
>
>         if (data_len & 0x4) {
>                 hash64 ^= *(const uint32_t *)data8;
>                 data8 += 4;
>         }
>
>         int bit_offset = 0;
>
>         if (data_len & 0x2) {
>                 hash64 ^= *(const uint16_t *)data8;
>                 bit_offset = 16;
>                 data8 += 2;
>         }
>
>         if (data_len & 0x1)
>                 hash64 ^= *(const uint8_t *)data8 << bit_offset;
>
>         hash32 = (hash64 >> 32) ^ (uint32_t)hash64;
>
>         return rte_be_to_cpu_32(hash32) ^ init_val;
> }
>
> What do you think?
>
> Also, consider to check in hash_functions_autotest keys with length equal
> to 3 (or eq 3 mod 4, for example 7 or 11)
>
> вт, 21 февр. 2023 г. в 19:37, Bili Dong <qobilidop@gmail.com>:
>
>> An XOR32 hash is needed in the Software Switch (SWX) Pipeline for its
>> use case in P4. We implement it in this patch so it could be easily
>> registered in the pipeline later.
>>
>> Signed-off-by: Bili Dong <qobilidop@gmail.com>
>> ---
>>  .mailmap                       |  1 +
>>  app/test/test_hash_functions.c | 33 +++++++++++--
>>  lib/hash/rte_hash_xor.h        | 87 ++++++++++++++++++++++++++++++++++
>>  3 files changed, 118 insertions(+), 3 deletions(-)
>>  create mode 100644 lib/hash/rte_hash_xor.h
>>
>> diff --git a/.mailmap b/.mailmap
>> index a9f4f28fba..3e9bec29d5 100644
>> --- a/.mailmap
>> +++ b/.mailmap
>> @@ -159,6 +159,7 @@ Bernard Iremonger <bernard.iremonger@intel.com>
>>  Bert van Leeuwen <bert.vanleeuwen@netronome.com>
>>  Bhagyada Modali <bhagyada.modali@amd.com>
>>  Bharat Mota <bmota@vmware.com>
>> +Bili Dong <qobilidop@gmail.com>
>>  Bill Hong <bhong@brocade.com>
>>  Billy McFall <bmcfall@redhat.com>
>>  Billy O'Mahony <billy.o.mahony@intel.com>
>> diff --git a/app/test/test_hash_functions.c
>> b/app/test/test_hash_functions.c
>> index 76d51b6e71..53e296fec4 100644
>> --- a/app/test/test_hash_functions.c
>> +++ b/app/test/test_hash_functions.c
>> @@ -15,6 +15,7 @@
>>  #include <rte_hash.h>
>>  #include <rte_jhash.h>
>>  #include <rte_hash_crc.h>
>> +#include <rte_hash_xor.h>
>>
>>  #include "test.h"
>>
>> @@ -22,8 +23,8 @@
>>   * Hash values calculated for key sizes from array "hashtest_key_lens"
>>   * and for initial values from array "hashtest_initvals.
>>   * Each key will be formed by increasing each byte by 1:
>> - * e.g.: key size = 4, key = 0x03020100
>> - *       key size = 8, key = 0x0706050403020100
>> + * e.g.: key size = 4, key = 0x00010203
>> + *       key size = 8, key = 0x0001020304050607
>>   */
>>  static uint32_t hash_values_jhash[2][12] = {{
>>         0x8ba9414b, 0xdf0d39c9,
>> @@ -51,6 +52,19 @@ static uint32_t hash_values_crc[2][12] = {{
>>         0x789c104f, 0x53028d3e
>>  }
>>  };
>> +static uint32_t hash_values_xor32[2][12] = {{
>> +       0x00000000, 0x00010000,
>> +       0x00010203, 0x04040404, 0x00000000, 0x00000000,
>> +       0x00000000, 0x00000000, 0x0c040404, 0x000d0e0f,
>> +       0x04212223, 0x04040404
>> +},
>> +{
>> +       0xdeadbeef, 0xdeacbeef,
>> +       0xdeacbcec, 0xdaa9baeb, 0xdeadbeef, 0xdeadbeef,
>> +       0xdeadbeef, 0xdeadbeef, 0xd2a9baeb, 0xdea0b0e0,
>> +       0xda8c9ccc, 0xdaa9baeb
>> +}
>> +};
>>
>>
>>  /*******************************************************************************
>>   * Hash function performance test configuration section. Each
>> performance test
>> @@ -61,7 +75,7 @@ static uint32_t hash_values_crc[2][12] = {{
>>   */
>>  #define HASHTEST_ITERATIONS 1000000
>>  #define MAX_KEYSIZE 64
>> -static rte_hash_function hashtest_funcs[] = {rte_jhash, rte_hash_crc};
>> +static rte_hash_function hashtest_funcs[] = {rte_jhash, rte_hash_crc,
>> rte_hash_xor32};
>>  static uint32_t hashtest_initvals[] = {0, 0xdeadbeef};
>>  static uint32_t hashtest_key_lens[] = {
>>         1, 2,                 /* Unusual key sizes */
>> @@ -85,6 +99,9 @@ get_hash_name(rte_hash_function f)
>>         if (f == rte_hash_crc)
>>                 return "rte_hash_crc";
>>
>> +       if (f == rte_hash_xor32)
>> +               return "rte_hash_xor32";
>> +
>>         return "UnknownHash";
>>  }
>>
>> @@ -173,6 +190,16 @@ verify_precalculated_hash_func_tests(void)
>>                                        hash_values_crc[j][i], hash);
>>                                 return -1;
>>                         }
>> +
>> +                       hash = rte_hash_xor32(key, hashtest_key_lens[i],
>> +                                       hashtest_initvals[j]);
>> +                       if (hash != hash_values_xor32[j][i]) {
>> +                               printf("XOR32 for %u bytes with initial
>> value 0x%x."
>> +                                      " Expected 0x%x, but got 0x%x\n",
>> +                                      hashtest_key_lens[i],
>> hashtest_initvals[j],
>> +                                      hash_values_xor32[j][i], hash);
>> +                               return -1;
>> +                       }
>>                 }
>>         }
>>
>> diff --git a/lib/hash/rte_hash_xor.h b/lib/hash/rte_hash_xor.h
>> new file mode 100644
>> index 0000000000..366adbe64c
>> --- /dev/null
>> +++ b/lib/hash/rte_hash_xor.h
>> @@ -0,0 +1,87 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(c) 2023 Intel Corporation
>> + */
>> +
>> +#ifndef _RTE_HASH_XOR_H_
>> +#define _RTE_HASH_XOR_H_
>> +
>> +/**
>> + * @file
>> + *
>> + * RTE XOR Hash
>> + */
>> +
>> +#ifdef __cplusplus
>> +extern "C" {
>> +#endif
>> +
>> +#include <stdint.h>
>> +
>> +#include <rte_byteorder.h>
>> +
>> +/**
>> + * Calculate XOR32 hash on user-supplied byte array.
>> + *
>> + * @param data
>> + *   Data to perform hash on.
>> + * @param data_len
>> + *   How many bytes to use to calculate hash value.
>> + * @param init_val
>> + *   Value to initialise hash generator.
>> + * @return
>> + *   32bit calculated hash value.
>> + */
>> +static inline uint32_t
>> +rte_hash_xor32(const void *data, uint32_t data_len, uint32_t init_val)
>> +{
>> +       uint32_t hash32;
>> +       const uint8_t *data8 = data;
>> +
>> +       /* Minimize byte order conversions depending on data length. */
>> +       if (data_len >= 8) {
>> +               /* For longer arrays, operate in big endian. */
>> +               uint64_t hash64 = rte_cpu_to_be_32(init_val);
>> +
>> +               uint32_t i;
>> +               for (i = 0; i < data_len / 8; i++) {
>> +                       hash64 ^= *(const uint64_t *)data8;
>> +                       data8 += 8;
>> +               }
>> +
>> +               if (data_len & 0x4) {
>> +                       hash64 ^= *(const uint32_t *)data8;
>> +                       data8 += 4;
>> +               }
>> +
>> +               hash32 = rte_be_to_cpu_32(hash64 ^ (hash64 >> 32));
>> +       } else {
>> +               /* For shorter arrays, operate in host endian. */
>> +               hash32 = init_val;
>> +
>> +               if (data_len & 0x4) {
>> +                       hash32 ^= rte_be_to_cpu_32(*(const uint32_t
>> *)data8);
>> +                       data8 += 4;
>> +               }
>> +       }
>> +
>> +       /* Deal with remaining (< 4) bytes. */
>> +
>> +       uint8_t bit_offset = 0;
>> +
>> +       if (data_len & 0x2) {
>> +               hash32 ^= (uint32_t)rte_be_to_cpu_16(*(const uint16_t
>> *)data8) << 16;
>> +               data8 += 2;
>> +               bit_offset += 16;
>> +       }
>> +
>> +       if (data_len & 0x1)
>> +               hash32 ^= (uint32_t)(*(const uint8_t *)data8) << (24 -
>> bit_offset);
>> +
>> +       return hash32;
>> +}
>> +
>> +#ifdef __cplusplus
>> +}
>> +#endif
>> +
>> +#endif /* _RTE_HASH_XOR_H_ */
>> --
>> 2.34.1
>>
>>
>
> --
> Regards,
> Vladimir
>

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