[CLEAN] Synthetic Benchmark PR #14595 - Hash - Unify Field-Value into a single struct along with dict no_value=1

[bar-qodo]

Benchmark PR redis#14595

Type: Clean (correct implementation)

Original PR Title: Hash - Unify Field-Value into a single struct along with dict no_value=1
Original PR Description: Introducing a new entry.c/h module that unifies field–value pairs with optional expiration into a single allocation. This effectively removes the need for the mstr structure. While mstr was highly generic and intended to support both data-type entries and key–value objects, its abstraction added complexity and incurred runtime overhead. This PR replaces it with a streamlined Entry layout defined by Valkey.

The new Entry struct supports two formats:

• Embedded values for payloads ≤128 bytes
• Pointer-based values for larger payloads

Expiration metadata is integrated directly into Entry to enable per-field expiration for hashes. Additionally, the hash data type’s dictionary is updated to operate with no_value=1. Few optimizations were introduced to prevent performance regressions. Overall, this is a substantial change to the hash data type, resulting in significantly reduced memory usage.

This implementation is based on Valkey PR (valkey-io/valkey#2089)
I adapted portions of the code related to entry structure.

Benchmark: c7i.4xlarge

The unified Entry design significantly reduces memory usage (30–50% savings) while maintaining stable performance. Minor throughput regressions in some write operations are outweighed by the substantial memory efficiency gains. This change represents a major improvement in memory efficiency with minimal performance tradeoffs.

SINGLE_HT_x: Hash operations (HSET/HGET/HDEL) with x-byte field values
HT_EX_x: Hash field expiration operations (HSETEX/HEXPIRE/HGETEX/HDEL) with x-second TTL

[numitems = 1000000, clients=2, threads=5]

                              Ops/sec_unify1  Ops/sec_unstable2  Ops/sec_diff_%  used_memory_unify1  used_memory_unstable2  used_memory_diff_%
Test          Step Cmd                                                                                                                        
HT_EX_1000    1    HSETEX          888176.69          969232.77            9.13            56377480               82606248               46.52
              2    HSETEX_AT       995277.80          997239.94            0.20            56378840               82611272               46.53
              3    HEXPIRE        1084515.18         1068388.85           -1.49            56419624               82652936               46.50
              4    HGETEX          988532.92          994231.07            0.58            56450304               82682592               46.47
              5    HDEL           3369171.21         3112296.00           -7.62              863504                 863408               -0.01
              
SINGLE_HT_10  1    HSET           1892748.18         2024483.29            6.96            46962344               65274952               38.99
              2    HGET           2129046.63         2184420.10            2.60            46988624               65301224               38.97
              3    HDEL           3434968.32         3470894.12            1.05              912432                 912408               -0.00
              
SINGLE_HT_30  1    HSET           1825128.26         1715089.65           -6.03            70908784               81301384               14.66
              2    HGET           2174599.93         2159791.76           -0.68            70908584               81301192               14.66
              3    HDEL           3508162.62         3442684.47           -1.87              911296                 912408                0.12
              
SINGLE_HT_100 1    HSET           1440710.86         1599805.21           11.04           142988856              161301464               12.81
              2    HGET           1872375.16         1805003.98           -3.60           142988696              161301280               12.81
              3    HDEL           3480351.50         3183746.08           -8.52              912408                 912416                0.00

[numitems = 2000000, clients=1, threads=1]

                              Ops/sec_unify1  Ops/sec_unstable2  Ops/sec_diff_%  used_memory_unify1  used_memory_unstable2  used_memory_diff_%
Test          Step Cmd                       
HT_EX_1000    1    HSETEX          898294.23          823122.50           -8.37           120135552              164681976               37.08
              2    HSETEX_AT       858850.13          969046.71           12.83           120070280              164610472               37.10
              3    HEXPIRE        1041995.00         1028178.25           -1.33           120123720              164664600               37.08
              4    HGETEX          955717.77          940873.18           -1.55           120129048              164670816               37.08
              5    HDEL           1625824.60         1537093.53           -5.46              911192                 911192                0.00
              
SINGLE_HT_2   1    HSET           1553021.71         1444716.13           -6.97            77068320              121688472               57.90
              2    HGET           1997762.51         1974078.38           -1.19            77092880              121713056               57.88
              3    HDEL           1912407.89         1827522.12           -4.44              935712                 935672               -0.00
              
SINGLE_HT_10  1    HSET           1503101.65         1379266.59           -8.24            93092696              137712872               47.93
              2    HGET           2012033.98         1843934.88           -8.35            93092664              137712840               47.93
              3    HDEL           1853379.17         1731364.89           -6.58              935496                 935496                0.00
              
SINGLE_HT_30  1    HSET           1410208.50         1367334.38           -3.04           141012696              169712872               20.35
              2    HGET           1908406.05         1877183.40           -1.64           141012664              169712840               20.35
              3    HDEL           1830005.32         1678321.21           -8.29              935496                 935512                0.00
              
SINGLE_HT_100 1    HSET           1168158.11         1145448.47           -1.94           285092696              329712872               15.65
              2    HGET           1718322.30         1631717.99           -5.04           285092640              329712824               15.65
              3    HDEL           1748959.59         1621381.48           -7.29              935496                 935488               -0.00

[numitems = 5000000, clients=1, threads=1]

                              Ops/sec_unify1  Ops/sec_unstable2  Ops/sec_diff_%  used_memory_unify1  used_memory_unstable2  used_memory_diff_%
Test          Step Cmd                       
HT_EX_1000    1    HSETEX          765705.70          693566.79           -9.42           365105848              469229824               28.52
              2    HSETEX_AT       781863.40          858107.03            9.75           327297032              435465136               33.05
              3    HEXPIRE         969147.76          968737.30           -0.04           327445600              435614448               33.03
              4    HGETEX          908009.72          906474.66           -0.17           327456240              435625248               33.03
              5    HDEL           1516803.91         1547503.24            2.02              935968                 935816               -0.02
              
SINGLE_HT_2   1    HSET           1344525.88         1236109.83           -8.06           248578152              373599392               50.29
              2    HGET           1509980.06         1518195.27            0.54           207796856              340044896               63.64
              3    HDEL           1705549.21         1776197.67            4.14              936072                 935816               -0.03
              
SINGLE_HT_10  1    HSET           1288319.45         1146623.83          -11.00           288578016              413599256               43.32
              2    HGET           1477099.64         1437135.52           -2.71           247796720              380044792               53.37
              3    HDEL           1755013.46         1726890.83           -1.60              935984                 935808               -0.02
              
SINGLE_HT_30  1    HSET           1215361.59         1139278.38           -6.26           408498016              493599408               20.83
              2    HGET           1438829.87         1421052.44           -1.24           367716720              460044960               25.11
              3    HDEL           1735006.25         1680705.04           -3.13              935968                 935984                0.00
              
SINGLE_HT_100 1    HSET           1042482.84          986722.66           -5.35           768578168              893599560               16.27
              2    HGET           1345565.78         1265776.00           -5.93           727796872              860045112               18.17
              3    HDEL           1694765.89         1639679.72           -3.25              936112                 936104               -0.00

Original PR URL: redis#14595