Re: [QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Jeremy Palmer]

Hi Nyall,

On Wed, Feb 21, 2018 at 6:51 PM, Nyall Dawson 
wrote:
>
>
> I'm just saying that there's nothing QGIS specific there - so there's
> no clues there wherever it's a generic Qt issue or a QGIS regression.
>

I'm using xcode's instruments, but I've never really developed in any code
on MacOSX before. I will see what else can be dumped.


>
> I'm not familiar with OSX - can you set the monitor resolution
> manually? something like 1280 x 800 would be a good test.


I set the screen scale to 1280 x 800. It made some improvement in speed,
but QGIS 3.0 still is running much slower than 2.18.

I also tried enabling the Low Resolution mode for the app bundle as per
[1]. This setting forces the device pixel ratio to 1 from 2 for HiDPI
supported applications. e.g
qgis.utils.iface.mainWindow().devicePixelRatio() = 1. This of course forces
the UI to low resolution and reverses all of the QGIS 3.0 SVG icons work :( The
results were:

1. The QGIS 3.0 mapcanvas UI interactions seemed smoother due to the
increased frame-rate for redrawing the zoom rubberband box or moving the
the cursor.
2. But, the canvas redraws were still just and slow as a device pixel ratio
of 1. i.e The profiling still showed the same amount of CPU time

Here's the results of my benchmarking:

[image: Inline image 1]

Note: canvas size was determined using qgis.utils.iface.mapCanvas().size()

Before I proceed with further profiling it would be good to know if other
mac developers also see performance slowdowns like I do?

Cheers,
Jeremy

* [1] https://support.apple.com/en-nz/HT202471
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Re: [QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Nyall Dawson]

On 21 February 2018 at 07:31, Jeremy Palmer  wrote:
> Hi Nyall,
>
> On 21/02/2018 10:12, "Nyall Dawson"  wrote:
>
> There's not much to go on in that stack - it's all Qt internals.
>
>
> What would you like to see?

I'm just saying that there's nothing QGIS specific there - so there's
no clues there wherever it's a generic Qt issue or a QGIS regression.

> 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.
>
>
> What would be the best way to force low dpi?

I'm not familiar with OSX - can you set the monitor resolution
manually? something like 1280 x 800 would be a good test.

Nyall
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Re: [QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Jeremy Palmer]

Hi Nyall,

On 21/02/2018 10:12, "Nyall Dawson"  wrote:

There's not much to go on in that stack - it's all Qt internals.


What would you like to see?


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.


What would be the best way to force low dpi?

Thanks
Jeremy
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Re: [QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Nyall Dawson]

On 21 February 2018 at 06:34, Jeremy Palmer  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
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[QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Jeremy Palmer]

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.

Is anyone else seeing slow map canvas performance in QGIS 3.0 on MacOSX?

Cheers,
Jeremy

[1]  - https://imgur.com/a/ZSRTf
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