[Libreoffice-bugs] [Bug 51989] PDF export performance decreased in 3.6, exponentially depending on file size

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=51989

--- Comment #7 from Roman Eisele <bugs at eikota.de> 2012-07-15 11:10:44 PDT ---
Created attachment 64232
  --> https://bugs.freedesktop.org/attachment.cgi?id=64232
Big book sample (3222 pp. .odt file in book typography, German, no images,
graphics or tables, fonts included)

Update:
The decrease in PDF export performance does NOT (only) depend on
images/graphics, it is measurable even with .odt files containing formatted
text only, and it does depend exponentially on the .odt file size (count of
pages, etc.): when you export a big .odt file to PDF, you will notice an even
bigger decrease of performance.

Test:
To test with a real text sample (I am a bit distrustful about the value of
tests with mere placeholder texts), I created a 3222 pp. .odt sample file in
book typography -- no images, no graphics, no tables, only much German text,
some nice formatting with a bit of color, using (semi-)professional fonts and
styles. (If you wonder which text is free of copyright, but 3222 pp. long: it
is the Bible in Luther's original 1545 German translation ;-) The .odt file is
1.9 MB in size. You find it together with the (free) fonts attached to this bug
report.

To test I just open the file, do nothing else, do not even scroll, just select
"File > Export as PDF...", leave most settings at default, just select
 * General: "Export bookmarks"
 * General: "Export automatically inserted blank pages"
 * General: "Embed standard fonts"
 * Links:   "Export bookmarks as named destinations"
but don't select General: "Embed OpenDocument file",
and click "Export".

Results:
I distinguish three stages of PDF export. In stage I, the progress bar is not
yet visible, but the cursor turns to the spinning cursor or watch (depending on
your OS, I suppose). In stage II, the progress bar is visible, but does not
work yet, i.e. does not show any progress. In stage III, the pogress bar shows
the progress of export. To distinguish these stages is important, because it
may reveal something about where the decrease of performance occurs.

All values are in seconds and the mean value of several tests with each
version.


                           LibO 3.4.6    LibO 3.5.53    LibO 3.6.0.1
========================================================================
Export stage I              50            52             50
(spinning cursor)
------------------------------------------------------------------------
Exporr stage II              5             5            267 (!!!)
(progress bar visible,
but disabled)
------------------------------------------------------------------------
Export stage III           102           113            140
(progress bar
showing progress)
========================================================================
Total                      157           170            457 (!!!)


You see, we have a little decrease of performance in LibO 3.5.x as compared to
3.4.x, but a big decrease in LibO 3.6.0.1 as compared to both older versions.

The decrease happens partially in stage III of the export, but mostly in stage
II. This stage, which took only 5 seconds in LibO 3.4.x and 3.5.x, and is, with
small documents, so short that you may not even notice it, takes 267 seconds
now in LibreOffice 3.6.0.1. Wow! I already thought that LibO 3.6.0.1 freezed,
and this is really bad user experience. It seems that the duration of this
stage depends exponentially on file size, even without any graphics.

So the question is: WHAT does LibreOffice do in stage II? Here is the place of
the biggest regression of performance against LibreOffice 3.5.x, and here our
developers should look how to get performance back.

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