Thanks Nyall,
I have tested Hotspot and the result is interesting :
* 48.7% of the time is due to QgsRasterProjector::block that provide
projected raster block
* 26.6% of the time is due to ProjectorData::srcRowCol that identify the
source row col corresponding to the destination row col
Is some enhancement could e done here ?
Regards,
René-Luc
Le 05/10/2020 à 05:31, Nyall Dawson a écrit :
On Fri, 2 Oct 2020 at 00:53, René-Luc Dhont <[email protected]> wrote:
Hi devs,
A customer found that reading a lightweight GeoTIFF takes 1 second in
QGIS Server needs less than 200 milliseconds.
With timer I found somethings strange around the virtual
QgsRasterInterface block method and it's reimplation in QgsGdalProvider.
Here is part of my logs:
../src/core/raster/qgsrasteriterator.cpp:87 :
(readNextRasterPartInternal) [2ms] Entered
../src/core/providers/gdal/qgsgdalprovider.cpp:2641 : (initIfNeeded)
[1ms] GdalDataset opened
../src/core/providers/gdal/qgsgdalprovider.cpp:317 : (crsFromWkt) [0ms]
+proj=aea +lat_1=43 +lat_2=62 +lat_0=30 +lon_0=-30 +x_0=0 +y_0=0
+datum=WGS84 +units=m +no_defs
../src/core/providers/gdal/qgsgdalprovider.cpp:2836 : (initBaseDataset)
[0ms] GDALGetRasterNoDataValue = -3.4e+38
../src/core/providers/gdal/qgsgdalprovider.cpp:647 : (block) [10ms]
QgsGdalProvider::block
../src/core/providers/gdal/qgsgdalprovider.cpp:718 : (readBlock) [0ms]
QgsGdalProvider::readBlock
../src/core/providers/gdal/qgsgdalprovider.cpp:965 : (readBlock) [2ms]
QgsGdalProvider::readBlock completed in (seconds): 0.002
../src/core/providers/gdal/qgsgdalprovider.cpp:684 : (block) [0ms]
QgsGdalProvider::block completed in (seconds): 0.002
../src/core/raster/qgsrasteriterator.cpp:137 :
(readNextRasterPartInternal) [643ms] Raster iterator read next block
completed in (seconds): 0.656
../src/core/raster/qgsrasteriterator.cpp:87 :
(readNextRasterPartInternal) [3ms] Entered
../src/core/providers/gdal/qgsgdalprovider.cpp:647 : (block) [6ms]
QgsGdalProvider::block
../src/core/providers/gdal/qgsgdalprovider.cpp:718 : (readBlock) [0ms]
QgsGdalProvider::readBlock
../src/core/providers/gdal/qgsgdalprovider.cpp:965 : (readBlock) [0ms]
QgsGdalProvider::readBlock completed in (seconds): 0
../src/core/providers/gdal/qgsgdalprovider.cpp:684 : (block) [0ms]
QgsGdalProvider::block completed in (seconds): 0
../src/core/raster/qgsrasteriterator.cpp:137 :
(readNextRasterPartInternal) [283ms] Raster iterator read next block
completed in (seconds): 0.289
../src/core/raster/qgsrasteriterator.cpp:87 :
(readNextRasterPartInternal) [0ms] Entered
The qgsrasterinterator.cpp ligne 130 [1] tooks almost 300 times longer
than it's reimplementation.
Do you know a way to enhance this ?
I'd caution against reading too much into the debug output timings. My
suggestion is to re-run the tests using hotspot
(https://github.com/KDAB/hotspot) as this will give much more useful
information about the bottlenecks.
Nyall
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