RFR: 8265448: (zipfs): Reduce read contention in ZipFileSystem [v2]

[Alan Bateman]

On Wed, 5 May 2021 15:49:00 GMT, Lance Andersen <lancea at openjdk.org> wrote:

>> src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java line 2223:
>> 
>>> 2221:                 synchronized (zfch) {
>>> 2222:                     n = zfch.position(pos).read(bb);
>>> 2223:                 }
>> 
>> @LanceAndersen Are you planning to look at this? Do you mind checking the async close case to make sure that the synchronization isn't masking anything?
>> 
>> Also just to point out that pattern matching for instanceof ca be used here.
>
> Yes, I plan to look at this.  It would also be good to have a couple of additional reviews as well :-)

I think using the positional read on the underlying FileChannel is okay. I'm puzzled by the previous code as I would have expected it to restore the position (make me wonder if there are zipfs tests for this).

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PR: https://git.openjdk.java.net/jdk/pull/3853