perf: Pre-size the MSET command buffer from argument count - #2861
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redis_mset_cmd built the command into a smart_string that starts at 256 bytes and grows to the next 4KB page on demand, so a high-arity MSET realloc'd (and recopied) the buffer once per ~4KB produced. The pair count is known up front, so reserve the buffer before the append loop. A cheap pre-pass sums each field's RESP framing, the configured key prefix, and the value length when it is already a string (non-strings get a fixed allowance). The estimate only reads types and lengths, so it cannot change the emitted bytes; under-estimating just falls back to the normal growth path. Same builder backs MSETNX. Verified on PHP 8.4: small and 2000-pair MSET round-trips, mixed-type and prefixed keys, serialized values that exceed the estimate (growth fallback), MSETNX, no leaks under report_memleaks, and testSetGet/ testMSetNX/testHashes.
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Yeah, make sense, there are few more items, I am just pulling things out of a local tree and trying to keep PRs small, hence the #. |
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redis_mset_cmdbuilds the command into asmart_stringthat grows to the next 4KB page on demand, so a high-arityMSETreallocs and recopies once per ~4KB. The pair count is known up front, so a cheap length-only pre-pass reserves the buffer before the append loop. The estimate only reads types/lengths, so it can't change the emitted bytes; under-estimating just falls back to normal growth. Same builder backsMSETNX; the pattern extends toZADD/HMSET/variadic-key commands if wanted.Verified on PHP 8.4: small and 2000-pair MSET round-trips, mixed types, prefix, serializer growth-fallback, MSETNX, no leaks, and testSetGet/testMSetNX/testHashes pass.