• Martin Möhrmann's avatar
    fmt: avoid allocation when formatting byte slice arguments with verb s · f36e92db
    Martin Möhrmann authored
    fmtBytes is in the top 10 callers of runtime.slicebytetostring according
    to Google wide profiling data.
    
    Avoid the string conversion of the input byte slice in fmtBytes by calling
    a newly added specialized fmtS function for byte slices.
    
    Expand tests for verb s with widths to test strings and byte slice arguments.
    
    SprintfTruncateString     157ns ± 4%     156ns ± 3%     ~     (p=0.122 n=20+20)
    SprintfTruncateBytes      188ns ± 2%     155ns ± 3%  -18.00%  (p=0.000 n=20+19)
    
    name                   old alloc/op   new alloc/op   delta
    SprintfTruncateString     16.0B ± 0%     16.0B ± 0%     ~     (all equal)
    SprintfTruncateBytes      64.0B ± 0%     16.0B ± 0%  -75.00%  (p=0.000 n=20+20)
    
    name                   old allocs/op  new allocs/op  delta
    SprintfTruncateString      1.00 ± 0%      1.00 ± 0%     ~     (all equal)
    SprintfTruncateBytes       2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=20+20)
    
    Change-Id: I461bf514d4232b39bd9c812f7faa4e5ef693a03b
    Reviewed-on: https://go-review.googlesource.com/c/145284
    Run-TryBot: Martin Möhrmann <martisch@uos.de>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarRob Pike <r@golang.org>
    f36e92db
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