On Tue, 18 Jun 2024 10:00:33 GMT, lingjun-cg <[email protected]> wrote:
>> ### Performance regression of DecimalFormat.format
>> From the output of perf, we can see the hottest regions contain atomic
>> instructions. But when run with JDK 11, there is no such problem. The
>> reason is the removed biased locking.
>> The DecimalFormat uses StringBuffer everywhere, and StringBuffer itself
>> contains many synchronized methods.
>> So I added support for some new methods that accept StringBuilder which is
>> lock-free.
>>
>> ### Benchmark testcase
>>
>> @BenchmarkMode(Mode.AverageTime)
>> @Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
>> @Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
>> @State(Scope.Thread)
>> @OutputTimeUnit(TimeUnit.NANOSECONDS)
>> public class JmhDecimalFormat {
>>
>> private DecimalFormat format;
>>
>> @Setup(Level.Trial)
>> public void setup() {
>> format = new DecimalFormat("#0.00000");
>> }
>>
>> @Benchmark
>> public void testNewAndFormat() throws InterruptedException {
>> new DecimalFormat("#0.00000").format(9524234.1236457);
>> }
>>
>> @Benchmark
>> public void testNewOnly() throws InterruptedException {
>> new DecimalFormat("#0.00000");
>> }
>>
>> @Benchmark
>> public void testFormatOnly() throws InterruptedException {
>> format.format(9524234.1236457);
>> }
>> }
>>
>>
>> ### Test result
>> #### Current JDK before optimize
>>
>> Benchmark Mode Cnt Score Error Units
>> JmhDecimalFormat.testFormatOnly avgt 50 642.099 ? 1.253 ns/op
>> JmhDecimalFormat.testNewAndFormat avgt 50 989.307 ? 3.676 ns/op
>> JmhDecimalFormat.testNewOnly avgt 50 303.381 ? 5.252 ns/op
>>
>>
>>
>> #### Current JDK after optimize
>>
>> Benchmark Mode Cnt Score Error Units
>> JmhDecimalFormat.testFormatOnly avgt 50 351.499 ? 0.761 ns/op
>> JmhDecimalFormat.testNewAndFormat avgt 50 615.145 ? 2.478 ns/op
>> JmhDecimalFormat.testNewOnly avgt 50 209.874 ? 9.951 ns/op
>>
>>
>> ### JDK 11
>>
>> Benchmark Mode Cnt Score Error Units
>> JmhDecimalFormat.testFormatOnly avgt 50 364.214 ? 1.191 ns/op
>> JmhDecimalFormat.testNewAndFormat avgt 50 658.699 ? 2.311 ns/op
>> JmhDecimalFormat.testNewOnly avgt 50 248.300 ? 5.158 ns/op
>
> lingjun-cg has updated the pull request incrementally with one additional
> commit since the last revision:
>
> 8333396: Performance regression of DecimalFormat.format
Using `<T extends Appendable & CharSequence> ` instead of `StringBuf` seems a
good idea, but it has a disadvantage. The `Appendable` defines only 3 `append`
methods which cannot cover some cases. For example, this method
`SimpleDateFormat#format(Date, StringBuffer, FieldDelegate)` contains the
following code:
case TAG_QUOTE_CHARS:
toAppendTo.append(compiledPattern, i, count);
i += count;
break;
It requires `append(char[], int, int)`, but the `Appendable` has no such method.
So it's difficult to use `<T extends Appendable & CharSequence> ` in methods
`String DateFormat.format(Date date), String ListFormat.format(List<String>
input) and, String MessageFormat.format(Object obj)`.
The method in `java.text.MessageFormat#subformat` contains the following code:
int argumentNumber = argumentNumbers[i];
if (arguments == null || argumentNumber >= arguments.length) {
result.append('{').append(argumentNumber).append('}');
continue;
}
It requires `append(int)`, but the `Appendable` has no such method.
To sum up
1. `<T extends Appendable & CharSequence> ` is clear, but lack of extensibility
2. StringBuf is not so clear, but it's more extensibility. We can add
`append(char[], int, int)` to `StringBuf` to support `SimpleDateFormat`.
3. New interface StringBuf no need to handle IOException, but use `<T extends
Appendable & CharSequence> ` need to add a lot of try...catch statements around
the append method.
4.
So it seems `StringBuf` is better if we want to fix the problem in
`DateFormat,ListFormat,MessageFormat` in unique way.
I look forward to your reply. @naotoj @liach @justin-curtis-lu
Using `<T extends Appendable & CharSequence> ` instead of `StringBuf` seems a
good idea, but it has a disadvantage. The `Appendable` defines only 3 `append`
methods which cannot cover some cases. For example, this method
`SimpleDateFormat#format(Date, StringBuffer, FieldDelegate)` contains the
following code:
case TAG_QUOTE_CHARS:
toAppendTo.append(compiledPattern, i, count);
i += count;
break;
It requires `append(char[], int, int)`, but the `Appendable` has no such method.
So it's difficult to use `<T extends Appendable & CharSequence> ` in methods
`String DateFormat.format(Date date), String ListFormat.format(List<String>
input) and, String MessageFormat.format(Object obj)`.
The method in `java.text.MessageFormat#subformat` contains the following code:
int argumentNumber = argumentNumbers[i];
if (arguments == null || argumentNumber >= arguments.length) {
result.append('{').append(argumentNumber).append('}');
continue;
}
It requires `append(int)`, but the `Appendable` has no such method.
To sum up
1. `<T extends Appendable & CharSequence> ` is clear, but lack of extensibility
2. StringBuf is not so clear, but it's more extensibility. We can add
`append(char[], int, int)` to `StringBuf` to support `SimpleDateFormat`.
3. New interface StringBuf no need to handle IOException, but use `<T extends
Appendable & CharSequence> ` need to add a lot of try...catch statements around
the append method.
So it seems `StringBuf` is better if we want to fix the problem in
`DateFormat,ListFormat,MessageFormat` in unique way.
I look forward to your reply. @naotoj @liach @justin-curtis-lu
-------------
PR Comment: https://git.openjdk.org/jdk/pull/19513#issuecomment-2177382329
PR Comment: https://git.openjdk.org/jdk/pull/19513#issuecomment-2177383927
