[QGIS-Developer] Qgis server: terrible performance with Qgis 3.26

[David Marteau]

May be I could use QgsRuntimeProfiler output in first place ?

Le 20/06/2022 à 18:55, Even Rouault a écrit :
>
> Use sysprof or just run under a debugger and interrupt regularly 
> should help you spot in which method(s) most time is spent
>
> Le 20/06/2022 à 18:48, David Marteau via QGIS-Developer a écrit :
>>
>> I used the following test:
>>
>> readflags = Qgis.ProjectReadFlags() readflags |= 
>> Qgis.ProjectReadFlag.TrustLayerMetadata|Qgis.ProjectReadFlag.DontLoad3DViews|Qgis.ProjectReadFlag.DontLoadProjectStyles 
>> prj = QgsProject()%timeit -n 1 
>> prj.read(f"{datapath}/france_parts3_26.qgs",readflags)
>>
>> 105 ms ± 18.5 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
>>
>> This improve the result  but we are still much higher that the 
>> loading time of 3.24: 15ms compared to 105ms
>>
>>
>> Le 20/06/2022 à 18:38, Nyall Dawson a écrit :
>>>
>>>
>>> On Mon, 20 June 2022, 11:42 pm David Marteau, <dmarteau at 3liz.com> wrote:
>>>
>>>     Hi,
>>>
>>>     > You should set the other new read optimisation flags here --
>>>     see
>>>     https://github.com/qgis/QGIS/blob/88ebb3f2f513dbce5a775f50e51ea0117f859c65/src/core/qgis.h#L1962
>>>
>>>     These are already available also in 3.24 and we use the  
>>>     `TrustLayerMetadata` in the above test. For server,  the other
>>>     flags are not applicable (Getprint requests need print layouts ).
>>>
>>>     So that mean we are comparing 3.24 to 3.26 with same level of
>>>     read optimisation and that does not change the fact that, for
>>>     that very same level of read optimisation, project's loading is
>>>     incredibly  slower in 3.26.
>>>
>>>
>>> You'll need to set the new flags relating to skipping the 3d views 
>>> and project style loading in order to compare properly. Neither of 
>>> those things were occurring in 3.24, and both have an associated 
>>> cost. And neither are relevant for server.
>>>
>>> Nyall
>>>
>>>
>>>
>>>     Le 20/06/2022 à 15:10, Nyall Dawson a écrit :
>>>>
>>>>
>>>>     On Mon, 20 June 2022, 9:37 pm David Marteau via QGIS-Developer,
>>>>     <qgis-developer at lists.osgeo.org> wrote:
>>>>
>>>>         Hi,
>>>>
>>>>         I have noticed a huge drop of performance while testing
>>>>         Qgis server with Qgis 3.26, from 10x to 30x slower as usual.
>>>>
>>>>         Trying to reduce the problem I have found a huge increase
>>>>         of time spend reading the project in 3.26 compared to 3.24.
>>>>
>>>>         Here some benchmark with very simple project from the test
>>>>         data set. Note: the project has been updated with qgis 3.26:
>>>>
>>>>         Qgis 3.24:
>>>>         ======
>>>>
>>>>         readflags = QgsProject.ReadFlags()readflags |=
>>>>         QgsProject.FlagTrustLayerMetadata
>>>>
>>>>         prj = QgsProject()
>>>>
>>>>         %timeit -n 1 prj.read(f"{datapath}/france_parts.qgs",readflags)
>>>>
>>>>         > 15.7 ms ± 205 µs per loop (mean ± std. dev. of 7 runs, 1 loop each)
>>>>
>>>>         Qgis 3.26:
>>>>         ======
>>>>
>>>>         readflags = QgsProject.ReadFlags() readflags |=
>>>>         QgsProject.FlagTrustLayerMetadata
>>>>
>>>>
>>>>     You should set the other new read optimisation flags here --
>>>>     see
>>>>     https://github.com/qgis/QGIS/blob/88ebb3f2f513dbce5a775f50e51ea0117f859c65/src/core/qgis.h#L1962
>>>>
>>>>     Nyall
>>>>
>>>>         ​prj = QgsProject()
>>>>
>>>>         %timeit -n 1 prj.read(f"{datapath}/france_parts.qgs",readflags)
>>>>
>>>>         195 ms ± 44 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
>>>>
>>>>         There is a factor x10 between Qgis 3.24 et Qgis 3.26 for
>>>>         the exact same project.
>>>>         This has serious impact on requests: landing page catalog
>>>>         request time increased from approximatevely 110ms to more
>>>>         than 3.0s with our test data set.
>>>>
>>>>
>>>>         David Marteau
>>>>         www.3liz.com <http://www.3liz.com>
>>>>
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>>
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