perf: Pre-size reply arrays where the element count is known#2855
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Several multibulk reply builders called array_init (8-bucket default) right after reading the element count off the wire, forcing one or more HashTable resizes as elements were appended. Switch these sites to array_init_size using the known count. The count is clamped to >= 0 because a null multibulk header yields -1, and array_init_size takes a uint32_t; a negative value would otherwise request a huge table. array_init_size(_, 0) is equivalent to array_init, so the clamp is never worse than the prior behavior. Covers redis_sock_read_multibulk_reply_zval, the LPOS COUNT path, CLIENT TRACKINGINFO, HELLO, and nested multibulk in the recursive variant reader.
michael-grunder
approved these changes
Jun 2, 2026
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Several multibulk reply builders called
array_init(8-bucket default) right after reading the element count off the wire, forcing HashTable resizes as elements were appended.Switch these sites to
array_init_sizewith the known count. The count is clamped to>= 0because a null multibulk header yields-1andarray_init_sizetakes auint32_t;array_init_size(_, 0)is equivalent toarray_init, so the clamp is never worse than before. Coversredis_sock_read_multibulk_reply_zval, the LPOS COUNT path, CLIENT TRACKINGINFO, HELLO, and nested multibulk in the recursive variant reader.Built on PHP 8.4; smoke tests exercise MULTI/EXEC and LPOS COUNT result arrays.