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Reporter: Trav [Submitted to the original trac issue database at 9.55am, Wednesday, 17th February 2010]
I'm not sure whether this is something that can/should be fixed in Meraartor or is actually really just a Qt bug, but when virtual nodes are enabled the download more function quickly gets exponentially slower as the number of features on the map increases.
From a UI perspective it shows as an inordinate amount of time at the "Parsing XML" step (it quickly becomes minutes even for downloads of only a few hundred metres square, turning off the virtual nodes feature returns the performance to normal.
Running callgrind indicates that the main culprit is QObjectPrivate::removePendingChildInsertedEvents(QObject*) which seems to be triggered by removing virtual nodes in Way::updateVirtuals().
I found this Qt bug report which appears to be related, although despite the claim of the problem being introduced in 4.6 GA I seem to be able to replicate the poor performance of destruction in Qt 4.3.4 (fedora 7 i386) as well as Qt 4.6.2 (Fedora 12 x86_64) http://bugreports.qt.nokia.com/browse/QTBUG-6546
This is all using a more or less current SVN build.
The text was updated successfully, but these errors were encountered:
Author: Koying [Added to the original trac issue at 1.26am, Thursday, 18th February 2010]
Could you give an order of magnitude (in number of features already in the document) before it becomes unbearable, please.
Just tried on Windows. Although it effectively becomes slower, which should be investigated, a download on a 50k features document do not seem unbearable.
OTOH, my box has 4Gb, and Merkaartor now uses 500Mb (with a 60Mb baseline at startup). On a box with less RAM, I can imagine it could become VERY slow because of malloc's... Take into account that the virtual nodes are not counted in the info box, so 50k displayed might really be 75k allocated...
Author: Trav [Added to the original trac issue at 2.13am, Thursday, 18th February 2010]
I've collected some very rough timings for download more of just the stage displayed as "Parsing XML" These are on a Core 2 Duo 1.83Ghz w/ 4Gb of RAM (running Fedora 12 64bit).
Reporter: Trav
[Submitted to the original trac issue database at 9.55am, Wednesday, 17th February 2010]
I'm not sure whether this is something that can/should be fixed in Meraartor or is actually really just a Qt bug, but when virtual nodes are enabled the download more function quickly gets exponentially slower as the number of features on the map increases.
From a UI perspective it shows as an inordinate amount of time at the "Parsing XML" step (it quickly becomes minutes even for downloads of only a few hundred metres square, turning off the virtual nodes feature returns the performance to normal.
Running callgrind indicates that the main culprit is QObjectPrivate::removePendingChildInsertedEvents(QObject*) which seems to be triggered by removing virtual nodes in Way::updateVirtuals().
I found this Qt bug report which appears to be related, although despite the claim of the problem being introduced in 4.6 GA I seem to be able to replicate the poor performance of destruction in Qt 4.3.4 (fedora 7 i386) as well as Qt 4.6.2 (Fedora 12 x86_64)
http://bugreports.qt.nokia.com/browse/QTBUG-6546
This is all using a more or less current SVN build.
The text was updated successfully, but these errors were encountered: