• haya14busa's avatar
    regexp: reduce allocs in regexp.Match for onepass regex · 8a16d7d4
    haya14busa authored
    There were no allocations in regexp.Match for *non* onepass regex
    because m.matchcap length is reset to zero (ncap=0 for regexp.Match).
    
    But, as for onepass regex, m.matchcap length remains as it is even when
    ncap=0 and it leads needless allocations.
    
    benchmark                                    old ns/op      new ns/op      delta
    BenchmarkMatch_onepass_regex/32-4      6465           4628           -28.41%
    BenchmarkMatch_onepass_regex/1K-4      208324         151558         -27.25%
    BenchmarkMatch_onepass_regex/32K-4     7230259        5834492        -19.30%
    BenchmarkMatch_onepass_regex/1M-4      234379810      166310682      -29.04%
    BenchmarkMatch_onepass_regex/32M-4     7903529363     4981119950     -36.98%
    
    benchmark                                    old MB/s     new MB/s     speedup
    BenchmarkMatch_onepass_regex/32-4      4.95         6.91         1.40x
    BenchmarkMatch_onepass_regex/1K-4      4.92         6.76         1.37x
    BenchmarkMatch_onepass_regex/32K-4     4.53         5.62         1.24x
    BenchmarkMatch_onepass_regex/1M-4      4.47         6.30         1.41x
    BenchmarkMatch_onepass_regex/32M-4     4.25         6.74         1.59x
    
    benchmark                                    old allocs     new allocs     delta
    BenchmarkMatch_onepass_regex/32-4      32             0              -100.00%
    BenchmarkMatch_onepass_regex/1K-4      1024           0              -100.00%
    BenchmarkMatch_onepass_regex/32K-4     32768          0              -100.00%
    BenchmarkMatch_onepass_regex/1M-4      1048576        0              -100.00%
    BenchmarkMatch_onepass_regex/32M-4     104559255      0              -100.00%
    
    benchmark                                    old bytes      new bytes     delta
    BenchmarkMatch_onepass_regex/32-4      512            0             -100.00%
    BenchmarkMatch_onepass_regex/1K-4      16384          0             -100.00%
    BenchmarkMatch_onepass_regex/32K-4     524288         0             -100.00%
    BenchmarkMatch_onepass_regex/1M-4      16777216       0             -100.00%
    BenchmarkMatch_onepass_regex/32M-4     2019458128     0             -100.00%
    
    Fixes #19573
    
    Change-Id: I033982d0003ebb0360bb40b92eb3941c781ec74d
    Reviewed-on: https://go-review.googlesource.com/38270
    Run-TryBot: Michael Matloob <matloob@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: default avatarBrad Fitzpatrick <bradfitz@golang.org>
    8a16d7d4
exec_test.go 20.9 KB