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

[Vladimir Medvedkin <medvedkinv@gmail.com>]

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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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