<Swing Dev> [9] Review request for 8132791 No access to SynthContext.getContext()

[Alexander Scherbatiy]

Hello,

Could you review the fix:
   bug: https://bugs.openjdk.java.net/browse/JDK-8132791
   webrev: http://cr.openjdk.java.net/~alexsch/8132791/webrev.00


SynthContext is an object with 4 fields which is used a lot by Synth L&F 
for components painting. It has an internal API which allows to put 
unused objects to queue and reuse them later. Application developers 
will not be able to have access to this API in JDK 9 with modularization 
feature so they only be able to create new SyntContext objects. There 
are ways that a SyntContext object created by a developer can be 
disposed by Synth L&F and put to the unused object queue.  This can lead 
to a memory leak.

There are 2 options to fix the issue: provide a public API for the 
SyntContext object custom disposing or just get rid of the unused object 
queue.

Effective Java Guide has a suggestion: “avoiding object creation by 
maintaining your own object pool is a bad idea unless the objects in the 
pool are extremely heavyweight”

To check if there are memory or performance degradation for the second 
solution I used SwingMark application which extensively creates and 
paints a lot of Swing components like labels, menus and others.

The tests were run 5 times with using the object queue and without it.
There results can be found at: 
http://cr.openjdk.java.net/~alexsch/8132791/profiling/results_3-5

The minimum and maximum values from 5 runs are:

Tests which used an object queue:
used memory (in bytes)
   min: 3.75 million max: 3.78 million
heap size  (in bytes)
   min: 11.53 million max: 12.58 million
elapsed time (in milliseconds)
   min: 57.27 thousand max: 57.97 thousand
requests for SynthContext objects: 380 thousands
created objects: 21

Tests which did not use an object queue:
used memory (in bytes)
   min:  3.71 million max: 3.79 million
heap size   (in bytes)
   min: 11.53 million max: 12.58 million
elapsed time (in milliseconds)
   min: 57.90 thousand max: 57.97 thousand
requests for SynthContext objects: 380 thousands
created objects: 380 thousands

There were about 380 thousand request for SynthContext objects in both 
tests but only 21 object were crated for the first ones.

However, the used memory size and running time are nearly the same for 
both runs for these particular tests.

According to the test results it looks reasonable to remove the custom 
object pool support from the SynthContext object.

Thanks,
Alexandr.