The sorted array binary search implementation no longer uses the inline
cache array, so remove all MRB_INLINE_METHOD_CACHE definitions and
related code.
By replacing the open‐addressing hash with a sorted array and binary
search, we eliminate tombstone management and improve cache locality of
method entries. This preserves the original contiguous values+keys
layout and peak memory usage, while simplifying growth logic and
delivering lookup performance gains.
Preserve the original iv_tbl heap layout and allocation pattern, but
switch iv_put to maintain sorted keys and iv_get/iv_del to perform
binary search. This eliminates extra probing overhead, improves
read-heavy lookup performance for small tables, and incurs zero
additional allocations.
My previous attempts to improve method table (mt_tbl) performance by introducing a load factor and adjusting the initial allocation size unfortunately led to undesirable increases in memory consumption.
Given that memory usage is a primary concern, I've reverted the following changes:
- Removed the load factor based rehashing logic.
- Removed the related definitions for the load factor.
- Ensured the initial allocation size is 8.
This restores the method table to its original behavior, where it rehashes only when the table is completely full or during initial allocation. This should bring memory usage back to its baseline level prior to these optimization attempts.
The method table (mt_tbl) in src/class.c previously only rehashed when it became completely full. With linear probing, this could lead to significant performance degradation for lookups and insertions as the table approached full capacity.
This change introduces a load factor (MT_LOAD_FACTOR_NUM/MT_LOAD_FACTOR_DEN, set to 3/4 or 0.75). The mt_put function now checks if adding a new element would cause the table's size to meet or exceed this load factor relative to its allocated capacity. If so, it triggers a rehash before inserting the new element.
This helps maintain more empty slots in the hash table, improving the average-case performance of linear probing and reducing the likelihood of worst-case scenarios. The existing initial allocation size and doubling strategy for rehashing are retained.
mempool.h provide compatibility layer so that existing programs does not
need to update (but update recommended anyway, since compatibility layer
takes mrb_state that is not used at all).
Since mrb_calloc() (along with mrb_calloc) takes two arguments: nmemb
which is number of array elements, and size which is size of the array.
Of course, revsersing does not change the behavior, but we'd like to
respect the original design intention of calloc(3).
Along with removing mrb_state first argument from the function. From
mruby 3.2, this function is *not* the default function, but the entry
point that can be redefined for the application. The function in
`src/allocf.c` is the default *implementation* (using malloc / realloc /
free) of the function.
Since the function returns either callinfo or env, thus the name does
not describe the current behavior. In addition, we did some refactoring
on the function.
Yukihiro "Matz" Matsumoto