On Wed, 6 Sep 2023 13:36:22 GMT, Claes Redestad <redes...@openjdk.org> wrote:
> This PR seeks to improve formatting of hex digits using `java.util.HexFormat`
> somewhat.
>
> This is achieved getting rid of a couple of lookup tables, caching the result
> of `HexFormat.of().withUpperCase()`, and removing tiny allocation that
> happens in the `formatHex(A, byte)` method. Improvements range from 20-40% on
> throughput, and some operations allocate less:
>
>
> Name Cnt Base Error Test Error Unit
> Diff%
> HexFormatBench.appenderLower 15 1,330 ± 0,021 1,065 ± 0,067 us/op
> 19,9% (p = 0,000*)
> :gc.alloc.rate 15 11,481 ± 0,185 0,007 ± 0,000 MB/sec
> -99,9% (p = 0,000*)
> :gc.alloc.rate.norm 15 16,009 ± 0,000 0,007 ± 0,000 B/op
> -100,0% (p = 0,000*)
> :gc.count 15 3,000 0,000 counts
> :gc.time 3 2,000 ms
> HexFormatBench.appenderLowerCached 15 1,317 ± 0,013 1,065 ± 0,054 us/op
> 19,1% (p = 0,000*)
> :gc.alloc.rate 15 11,590 ± 0,111 0,007 ± 0,000 MB/sec
> -99,9% (p = 0,000*)
> :gc.alloc.rate.norm 15 16,009 ± 0,000 0,007 ± 0,000 B/op
> -100,0% (p = 0,000*)
> :gc.count 15 3,000 0,000 counts
> :gc.time 3 2,000 ms
> HexFormatBench.appenderUpper 15 1,330 ± 0,022 1,065 ± 0,036 us/op
> 19,9% (p = 0,000*)
> :gc.alloc.rate 15 34,416 ± 0,559 0,007 ± 0,000 MB/sec
> -100,0% (p = 0,000*)
> :gc.alloc.rate.norm 15 48,009 ± 0,000 0,007 ± 0,000 B/op
> -100,0% (p = 0,000*)
> :gc.count 15 0,000 0,000 counts
> HexFormatBench.appenderUpperCached 15 1,353 ± 0,009 1,033 ± 0,014 us/op
> 23,6% (p = 0,000*)
> :gc.alloc.rate 15 11,284 ± 0,074 0,007 ± 0,000 MB/sec
> -99,9% (p = 0,000*)
> :gc.alloc.rate.norm 15 16,009 ± 0,000 0,007 ± 0,000 B/op
> -100,0% (p = 0,000*)
> :gc.count 15 3,000 0,000 counts
> :gc.time 3 2,000 ms
> HexFormatBench.toHexLower 15 0,198 ± 0,001 0,119 ± 0,008 us/op
> 40,1% (p = 0,000*)
> :gc.alloc.rate 15 0,007 ± 0,000 0,007 ± 0,000 MB/sec
> -0,0% (p = 0,816 )
> :gc.alloc.rate.norm 15 0,001 ± 0,000 0,001 ± 0,000 B/op
> -40,1% (p = 0,000*)
> :gc.count 15 0,000 0,000 ...
src/java.base/share/classes/java/util/HexFormat.java line 644:
> 642: return (char)('a' - 10 + value);
> 643: }
> 644: return (char)('A' - 10 + value);
Not sure if this would adversely impact performance, but what about factoring
out these lines in a private method? They are repeated in `toHighHexDigit`.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/15591#discussion_r1317472587
