RFR: 4926314: Optimize Reader.read(CharBuffer) [v4]

[Philippe Marschall]

On Sun, 10 Jan 2021 01:59:18 GMT, Brett Okken <github.com+2996845+bokken at openjdk.org> wrote:

>> Philippe Marschall has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add unit tests
>>   
>>   - add unit test for Reader#read(CharBuffer)
>>   - add unit test for InputStreamReader#reader(CharBuffer)
>>   - test with both on-heap and off-heap buffers
>
> src/java.base/share/classes/java/io/Reader.java line 198:
> 
>> 196:         } else {
>> 197:             int remaining = target.remaining();
>> 198:             char cbuf[] = new char[Math.min(remaining, TRANSFER_BUFFER_SIZE)];
> 
> Would there be value in making this a (lazily created) member variable? That would allow a single instance to be reused. It seems likely that, if one call is made with a direct CharBuffer, subsequent calls will also be made with direct instances (probably same instance?).

I am not sure. It would help to reduce the allocation rate when reading a large amount of data into a small direct CharBuffer. I don't know how common that is. We would introduce an instance variable for one path in one method.

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PR: https://git.openjdk.java.net/jdk/pull/1915