[v25.3.x] iobuf: fix operator<=> and operator== for string_view comparisons#29477
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rockwotj merged 3 commits intoredpanda-data:v25.3.xfrom Jan 31, 2026
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The previous implementation had inverted stop_iteration logic - it stopped when the comparison was equal and continued when not equal, causing incorrect results when the first fragment comparison determined the ordering. Replaced iterator_consumer pattern with a simpler for-each loop over fragments. Added comprehensive tests covering multi-fragment comparisons. Benchmark results (instructions, runtime): - sv_cmp_0000: 49 -> 36 inst (-27%), 2.28ns -> 2.16ns (-5%) - sv_cmp_0001: 87 -> 64 inst (-26%), 3.61ns -> 3.17ns (-12%) - sv_cmp_1024 (different): 121 -> 60 inst (-50%), 4.98ns -> 3.44ns (-31%) - sv_cmp_1024 (same): 256 -> 214 inst (-16%), 10.37ns -> 9.41ns (-9%) Runtime improvements are consistent with instruction count reductions. (cherry picked from commit aad9cff)
Simplify operator== by delegating to the fixed operator<=> implementation. This reduces code duplication and ensures consistent comparison behavior. Benchmark results (instructions, runtime): - sv_eq_0000: 38 -> 30 inst (-21%), 2.30ns -> 1.95ns (-15%) - sv_eq_0001: 83 -> 58 inst (-30%), 3.61ns -> 2.96ns (-18%) - sv_eq_1024 (different): 80 -> 57 inst (-29%), 3.70ns -> 3.25ns (-12%) - sv_eq_1024 (same): 247 -> 209 inst (-15%), 10.50ns -> 9.46ns (-10%) Runtime improvements are consistent with instruction count reductions. (cherry picked from commit 30220a4)
Add sv_eq_* and sv_cmp_* benchmark cases to measure performance of iobuf::operator== and operator<=> against string_view. Uses a templated cmp_bench function with rhs_type parameter to support both iobuf-vs-iobuf and iobuf-vs-string_view comparisons. Tests both single-fragment and fragmented iobufs at sizes 0, 1, 1024. (cherry picked from commit 5752502)
rockwotj
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Jan 31, 2026
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Backport of PR #29461