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From Andreas Delmelle <andreas.delme...@telenet.be>
Subject Re: Fop 0.20.5 vs Fop Trunk Performace
Date Wed, 13 Feb 2008 20:15:52 GMT
On Feb 12, 2008, at 21:10, Puppala, Kumar (LNG-CON) wrote:

Hi Kumar

> >
> > Just to be sure: which revision of the trunk are you trying out?
>
> I obtained the latest from the trunk on Jan 22nd. Information  
> pertaining to the fopTrunk as seen in the status.xml file is:
> “status.xml 614201 2008-01-22 14:02:27Z jeremias”

OK, I think you can safely update this to the latest. Not that it  
will matter much.

>
> <snip />
> Yes, I am instantiating FopFactory just once. Initially I was not  
> doing that but I changed my code to instantiate it just once. The  
> results provided are with the change.

>
> > Apart from that, focusing purely on FOP Trunk, if you know how to
> > narrow it down to specific methods/calls that cause the increase in
> > processing time that would help us a lot.

> I do have the complete Heap report. Some of the classes having  
> maximum instances are as shown below:

Well, it's not so much the number of objects I'm thinking of, but  
rather, how much time is spent executing specific methods and which  
ones take longer in later iterations. The actual cause of the  
slowdown may precisely be located in a class of which there are  
relatively few instances alive, if I judge correctly. Or did you  
already check whether the bulk of the increase in processing-time is  
really only spent on garbage-collection?

> 463132 instances of class org.apache.fop.traits.MinOptMax
> 441537 instances of class org.apache.fop.layoutmgr.NonLeafPosition
<snip />
>
> I am not sure if this is something expected.

Is this an overall total, or a snapshot taken at a given point? These  
are figures I'd expect for a rather large page-sequence...

> Small question: Did you, by any chance, also try different JVM
> versions? Different platform?
>
> No. I can try on jre1.6.0_04. Since we are running the current FOP  
> on Solaris platform, we are performing our tests on Solaris.
>
> > Do you know which XML parser / XSLT processor gets used at runtime?
>
> We do not use an XSLT processor. We generate the FO file using an  
> in-house application and feed it to the FOP Server. Since I am  
> using the default handler, I think it’s using SAX Parser behind the  
> scenes.

Right, now I remember you already mentioned this earlier.

> <snip />
> In local tests I ran here, with two concurrent threads and a shared
> FopFactory instance, the processing time remains quite stable for me
> (test run on Apple JVM 1.5 using a  document that generates two page-
> sequences (=2+69 pages; the larger page-sequence contains forced
> breaks for each page))`

> My tests are much more diverse. Each iteration contains about 120  
> testcases. Each testcase targets a specific feature that we use.  
> Hence each such iteration covers most of the features like tables,  
> cells, images, big documents, rowspanning, columnSpanning, dual  
> column layout etc… In total I would say I am generating about 3000  
> pages per iteration. When comparing the results, I am comparing  
> them after each such iteration for about 15 times and I am seeing a  
> gradual increase in processing times.

Interesting. Can you somehow dump the testcases as a set of physical  
FO files, and make that available somewhere? This would make it  
possible for us to run the same tests locally, and investigate further.

If this is impossible for you, then I'd advise to start with a  
drastically trimmed-down version of your test-suite, and gradually  
change and/or increase the number of tests. See if you can isolate  
the problem to a specific set of files (tables? markers? custom  
fonts? etc.) At least that will give us a clue on where to start  
looking. What may also prove valuable is to try the tests using a  
different renderer.

One more remark:
> > 2)       I do see a lot of garbage collection happening in the new
> > FOP. The collection times are also very high.

As I already hinted at, this is not bad per se. This could simply  
indicate that FOP Trunk offers the GC more opportunities to clean up,  
so as to reduce the average footprint (when looking at it like a  
series of snapshots). Memory-consumption vs. processing-speed is  
virtually always a trade-off: the less info is cached, the more  
computations need to be performed multiple times, but a calculator  
that caches /all/ results and /never/ makes the same computation  
twice, requires an insane amount of memory...

That said, it still remains strange that the processing time  
increases with the number of runs... Can you try leaving the  
iterations running into the hundreds or thousands? Does the time keep  
increasing? By the same amount?

> <snip />
> Come to think of it: are your images stored on a local disk, or is
> there any network traffic involved that might explain the increasing
> lag...?

> The images are stored on local disk. However, I do see better  
> results for testcases containing Images and hence I do not believe  
> that there are any network traffic issues involved.

Sorry, I did not mean 'images' but more generally 'documents'. Are  
the input/output files all located on the same machine, or does some  
of it come from/end up on different machines? If so, are these  
machines dedicated to serving the I/O requests for your FOP process,  
or are they used for other processes as well?


Cheers

Andreas
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