On 21 February 2018 at 06:34, Jeremy Palmer <[email protected]> wrote: > Hi All, > > For some time I've been noticing that QGIS 3.0 on MacOSX has sluggish canvas > redraw speeds. When comparing between QGIS 2.18 and 3.0 I see ~4x more CPU > activity in 3.0 when performing the same set of operations on the same > dataset. > > My test case was using a single raster VRT with overviews, and zooming in > and panning around the map cavnas for 20 sec. On average each time I tested > this case the total used CPU time for 2.18 was about 6 secs, but in > 3.0dev-64369f8099 (complied against QT 5.10.0 with homebrew) I get total CPU > time of 25 secs. In QGIS 3.0 most of the time the application is using 100% > CPU (one core) and spikes to about 180-200% CPU when the canvas redraws are > performed. When using a profiler it seems much of the time is taken up in > QImage::copy(QRect const&) within two seperate, but equivalent, call > subtrees. See [1] for more info.
There's not much to go on in that stack - it's all Qt internals. Are you sure this isn't solely due to the fact that QGIS is painting so many more pixels? I'd like to see a test where you force a low dpi resolution for both 2.18 and 3.0. Nyall _______________________________________________ QGIS-Developer mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
