[SCIFIO] SCIFIO does not seem to release memory of closed images

[Burkhard Höckendorf]

Dear List,

First of all thanks for developing scifio and doing that open source. I 
have started to use it with ImageJ, since Fiji now offers the option to 
use it. Having said that, I may also have stumbled upon an issue. I'm 
unsure when (or whether) scifio releases the corresponding memory after 
images are closed. To look at this in a somewhat systematic way, I ran a 
macro (see below) to repeatedly open and close a 3GB single file 
uncompressed TIFF stack (2048x2048x367x16bits) and record some 
performance stats along the way. I ran this using a new download of Fiji.

Here are the results with scifio disabled:
      11450 ms to open files
   28578184 mem before opening files
9282667288 mem after opening files
9272732560 mem after opening files & GC
9272780080 mem after closing files
   24220936 mem after closing files & GC

And here with scifio enabled:
       43715 ms to open files
    26765224 mem before opening files
10517954400 mem after opening files
  9327459480 mem after opening files & GC
  9327506440 mem after closing files
  9314822896 mem after closing files & GC

I have also checked, whether memory is freed a couple of minutes after 
closing the images, which does not appear to be the case.

Note that scifio is also somewhat slower, although I'm a bit hesitant to 
bring this up, because it is still relatively young and I can see a few 
"improve ... performance" tickets in the issue tracker.

Below is the macro.
Kind regards,
Burkhard


nOpenTimes = 3;
file = "/path/to/stack";

run("Collect Garbage");
memBefore = IJ.currentMemory();

msToOpen = getTime();
for (i=0; i<nOpenTimes; i+=1) {
	open(file);
}
msToOpen = getTime() - msToOpen;

memFilesOpen = IJ.currentMemory();
run("Collect Garbage");
memFilesOpenGC = IJ.currentMemory();

for (i=0; i<nOpenTimes; i+=1) {
	close();
}
memFilesClosed = IJ.currentMemory();
run("Collect Garbage");
memFilesClosedGC = IJ.currentMemory();

print(""+ msToOpen + " ms to open files");
print(""+ memBefore + " mem before opening files");
print(""+ memFilesOpen + " mem after opening files");
print(""+ memFilesOpenGC + " mem after opening files & GC");
print(""+ memFilesClosed + " mem after closing files");
print(""+ memFilesClosedGC + " mem after closing files & GC");