[Kstars-devel] more on memory usage

[Jason Harris]

Hello,

Some further experiments, but unfortunately no new insights.
I repeated Heiko's experiment of running KStars normally, and again with each 
star added twice in KStarsData::processStar().  The difference in memory 
usage between these two runs was 61 MB, implying 6.1e7/126,000 = 484 bytes 
per star.  This is 120 bytes larger than sizeof(StarObject).

I then modified the for-loop in KStarsData::readStarData() so that not all of 
the hipNNN.dat files were read.  I ran three times, reading 0, 1, and 2 of 
the star data files:

      0 stars, size = 39.068 MB
1000 stars, size = 39.804 MB  (736 Bytes per star)
2000 stars, size = 40.452 MB  (692 Bytes per star)

It's interesting that the effective size per star is lower for larger numbers 
of stars.  This could mean that there is some extra data associated with the 
list, but not with individual stars, or that the first 1000 stars really do 
take more memory (because more of them have names, perhaps).

To test this, I repeated the runs reading only 1 and 2 of the hipNNN.dat 
files, but I started at hip021.dat instead of hip001.dat.  None of the stars 
in hip021.dat or hip022.dat are named.  The result:

1000 stars, size = 39.708 MB  (640 Bytes per star)
5000 stars, size = 42.172 MB  (620 Bytes per star)

So, indeed the star names seem to add substantial memory, but we are still far 
above 364 Bytes per star.  Plus, the fact that loading the full list of 
126,000 stars results in only 484 Bytes per star seems to support the 
conclusion that the extra memory usage is (at least partially) not associated 
with individual stars, but with the aggregate list somehow.

I looked at the star-loading classes (FileSource and KSFileReader) for clues, 
but nothing appeared obviously wrong.  FileSource uses an array of QStrings, 
but these aren't dynamically allocated so that memory should be freed when 
the object is destructed, right?  What's the advantage to using an array 
here, rather than a QStringList?

Jason
-- 
KStars:  A K Desktop Planetarium
http://edu.kde.org/kstars