ZipFileSystem performance regression

[Claes Redestad]

Filed: https://bugs.openjdk.java.net/browse/JDK-8222532

I've marked the bug as potentially affecting the upcoming 11.0.3
release, since the issue that caused this regression is purportedly
being backported to that version.

/Claes

On 2019-04-16 14:21, Claes Redestad wrote:
> Both before and after this regression, it seems the default behavior is
> not to use a temporary file (until ZFS.sync(), which writes to a temp
> file and then moves it in place, but that's different from what happens
> with the useTempFile option enabled). Instead entries (and the backing
> zip file system) are kept in-memory.
> 
> The cause of the issue here is instead that no deflation happens until
> sync(), even when writing to entries in-memory. Previously, the
> deflation happened eagerly, then the result of that was copied into
> the zip file during sync().
> 
> I've written a proof-of-concept patch that restores the behavior of
> eagerly compressing entries when the method is METHOD_DEFLATED and the
> target is to store byte[]s in-memory (the default scenario):
> 
> http://cr.openjdk.java.net/~redestad/scratch/zfs.eager_deflation.00/
> 
> This restores performance of parallel zip to that of 11.0.2 for the
> default case. It still has a similar regression for the case where
> useTempFile is enabled, but that should be easily addressed if this
> looks like a way forward?
> 
> (I've not yet created a bug as I got too caught up in trying to figure
> out what was going on here...)
> 
> Thanks!
> 
> /Claes
> 
> On 2019-04-16 09:29, Alan Bateman wrote:
>> On 15/04/2019 14:32, Lennart Börjeson wrote:
>>> :
>>>
>>> Previously, the deflation was done when in the call to Files.copy, 
>>> thus executed in parallel, and the final ZipFileSystem.close() didn't 
>>> do anything much.
>>>
>> Can you submit a bug? When creating/updating a zip file with zipfs 
>> then the closing the file system creates the zip file. Someone needs 
>> to check but it may have been that the temporary files (on the file 
>> system hosting the zip file) were deflated when writing (which is 
>> surprising but may have been the case).
>>
>> -Alan