GPU/CPU usage problem - updateFromDisplayLink deadlock

[JustinGanzer]

Hello Mapbox community and team!

I'll be providing sample code of a ViewController with a MapView that when zoomed in to the lowest tiles and back up again somehow initiates a very odd behaviour starting with the Mapbox-iOS-SDK 5.1.0. Lower versions will not result in this error, higher versions such as 5.2.0 still do.
After zooming in and back out the gpu and cpu are constantly at roughly 60% usage and will never cease to go below this even though the I'm not interacting with the device in any way.

Due to the update being called over over, all MapAnnotations are constantly updated as well, which makes it impossible to use drag and drop as they flicker between the new and old position, which in comparison is only a minor inconvenience.

This error does not appear on an empty MapView. It only appears after adding a source and layer that I'd normally use to show icons on the map. I'll follow up this thread once I figure out what exactly is causing this issue. Do note however, that the very same code runs into no issues with any SDK version below 5.1.0 Hopefully someone can figure out what changed. As always, I'm happy to help try out whatever I can to help nail down the reason for error.

Steps to reproduce

1. Present the controller provided or any other with a MapView that includes a symbol style/layer
2. Zoom all the way in, Zoom all the way out
3. Go over to the performance logging and watch the never ending CPU/GPU usage

Expected behavior

MapView will stop rendering things once no more updates are made, such as movement.

Actual behavior

MapView is called/calls updateFromDisplayLink over and over.

Configuration

Mapbox SDK versions:
5.1.0+ and up
iOS/macOS versions:
Tested only on 12.3 and up, sorry i didn't have older versions available.
Device/simulator models:
iPhone 5S simulated with 12.3.1

Xcode version:
Version 10.2.1 (10E1001)

Here the inverted call stack:

Result in SDK versions 5.1.0 and up:

Result in SDK versions 5.0.0 and lower:

The ViewController which lets this error be reproduced every single time once zoomed in all the way and back out:

import Mapbox

class TestMapController: UIViewController, MGLMapViewDelegate {
    
    var mapView: MGLMapView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        mapView = MGLMapView(frame: view.bounds, styleURL: MGLStyle.lightStyleURL)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        mapView.tintColor = .darkGray
        mapView.delegate = self
        view.addSubview(mapView)
        
    }
    
    func mapView(_ mapView: MGLMapView, didFinishLoading style: MGLStyle) {
        let source = MGLShapeSource(identifier: "pictures", features: [], options: nil)
        let blueBoxImage = TestMapController.singleColoredImage(of: .blue, and: CGSize(width: 50, height: 50))
        style.setImage(blueBoxImage, forName: "picture")
        let layer = TestMapController.getLayer(for: source)
        style.addSource(source)
        style.addLayer(layer)
    }
    
    static func singleColoredImage(of color: UIColor, and size: CGSize) -> UIImage {
        let format = UIGraphicsImageRendererFormat()
        return UIGraphicsImageRenderer(size: size, format: format).image { (context) in
            color.setFill()
            context.fill(CGRect(origin: .zero, size: size))
        }
    }
    
    static func getLayer(for source: MGLShapeSource) -> MGLStyleLayer {
        let layer = MGLSymbolStyleLayer(identifier: "pictures", source: source)
        layer.iconAllowsOverlap = NSExpression(forConstantValue: true)
        layer.minimumZoomLevel = 6.0
        let nameOfPictures = "picture"
        let matching = "'\(nameOfPictures)', '\(nameOfPictures)'"
        let formatImageName = "MGL_MATCH(highlight, \(matching), '\(nameOfPictures)')"
        let functionImage = NSExpression(format: formatImageName)
        layer.iconImageName = functionImage
        layer.keepsIconUpright = NSExpression(forConstantValue: 1)
        let formatScale = "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1, %@)"
        layer.iconScale = NSExpression(format: formatScale, [6: 0.3, 11: 0.6, 14: 0.88])
        return layer
    }
}

[RomainQuidet]

Hi, we face the same bug and this is truly a huge issue. We can't upgrade to SDK 5.x+ anymore because of this bug and insets bug (already opened somewhere else).
Here is a test I ran with Instruments:
SDK: Mapbox 5.3.0
Device: iphone X 12.4.1

This issue is not present on SDK 5.0. It appears on 5.1 and still there in 5.3.0

[julianrex]

/cc @tmpsantos @alexshalamov

[julianrex]

Thanks for the report @JustinGanzer.

[RomainQuidet]

You're welcome. I deactivate user tracking so nothing should force the map to render once done. Tested on your sample app from the framework sources, seems that there is an infinite loop somewhere.
Once rendered, the framework ask again for a rendering loop... (see the renderTreeParameters where needsRepaint is true just after a rendering).

[RomainQuidet]

Seems that RenderOrchestrator::hasTransitions(TimePoint timePoint) always returns true with hasFadingTiles()from resources

[julianrex]

Thanks for the detailed investigation - what lat/lons are you zooming in/out on?

[RomainQuidet]

South West of Paris, France
48.8214267 / 2.1670292
Do you mean it's an issue with the tiles content ? We are using our custom tiles.

[julianrex]

Are you able to try with a default Mapbox style?

[RomainQuidet]

Doing it right now.
Done. With default Streets tiles, the CPU stay around 1% when not moving the map, even when user location is active. Sooooo it seems that the bug in the SDK is triggered by our tiles:
RenderOrchestrator::hasTransitions returns true on renderSources hasFadingTiles() from a hidden layer.
Same for @JustinGanzer : what tile / source do you use?

[julianrex]

Thanks @RomainQuidet, @pozdnyakov is now going to investigate.

[RomainQuidet]

I confirm that tile.holdForFade(); returns always true in the TilePyramid class, which is the source of the issue. We have a hidden layer displaying nothing, maybe this kind of tiles should not return true here.

[pozdnyakov]

@RomainQuidet Thank you very much for your report and the investigation! I am looking at the issue. Meanwhile, would it be possible for you to try out a preliminary fix at #15600 and tell if it helps? Thanks!

[RomainQuidet]

Of course I'll patch my version and see if the issue is still visible. Tomorrow for me it's the end of the day in France ;)

[JustinGanzer]

@RomainQuidet @julianrex , In the original post I provided a small ViewController with nothing but a MapView and a SymbolStyleLayer (which seems to be the cause for the reaction) inside. No matter what tiles or what style is used, the issue will arise once zoomed in and out again.
Without a custom layer this issue does not occur.

Thanks for the detailed investigation @RomainQuidet. It's a huge issue for us as well and hinders us from updating to 5.x.

[RomainQuidet]

Hi @pozdnyakov, your patch #15600 seems to work on my tests. I don't see anymore the dead loop consuming CPU.

[pozdnyakov]

@RomainQuidet Thanks! @JustinGanzer does #15600 solve the problem for you too?

[RomainQuidet]

bad news, I can't reproduce the issue on my demo app but on our production app, the renderer is still stuck in a loop using 100% CPU... And there is a memory issue associated, it's creating data until the app is killed by the system. I'm investigating.

@pozdnyakov This time the RenderOrchestrator::hasTransitions always returns true by placement->hasTransitions(timePoint)

[pozdnyakov]

@pozdnyakov This time the RenderOrchestrator::hasTransitions always returns true by placement->hasTransitions(timePoint)

That's a different issue, investigating..

[pozdnyakov]

@RomainQuidet could you give some more details on how to reproduce #15342 (comment) ?
What is the value of Placement::stale when the app is stuck?

[RomainQuidet]

I wish I could help you more on this one, but I can't reproduce it on my demo app. I'm trying.
According to my logs, stale is false.

[pozdnyakov]

My speculative guess is that placementChanged for some reason is always set to true in Placement::commit() and it is causing the problem. I could recommend the following:

1. comment out the code block under
   // add the opacities from the current placement, and copy their current values from the previous placement
   and see if it helps.

2. comment out the code block under
   // copy and update values from the previous placement that aren't in the current placement but haven't finished fading
   and see if it helps.

3. try out the patch from [core] Fix placement for updated buckets #15308 (as its removes implicit opacities modifications) and see if it helps.

[RomainQuidet]

Hi, Thanks for investigating this strange issue.
I'll try that tomorrow.

[RomainQuidet]

Hi, neither 1st nor 2nd suggestions work. I can't apply your #15308 patch on my 5.3.0 branch there is too many conficts from the master branch.
I don't know how to help you more.

[astojilj]

@RomainQuidet

Hi, we face the same bug and this is truly a huge issue. We can't upgrade to SDK 5.x+ anymore because of this bug and insets bug (already opened somewhere else).

What is the inset bug blocking the upgrade?

[RomainQuidet]

Hi, since release 5.1, insets are not working correctly in our app, see #15574 #15233 #15198

[astojilj]

Hi, since release 5.1, insets are not working correctly in our app, see #15574 #15233 #15198

Could you please submit an issue with problem description: which API is used and, if possible a video presenting the issue?
It is important to understand if it is related to #15574. In a way, #15233 is not describing issue - it is an analysis assumption about the cause.
As it could be related to multiple issues, e.g. 4026451 I would suggest to start analysis from issue description in order to get it fixed. Thanks.

[1ec5]

It is important to understand if it is related to #15574. In a way, #15233 is not describing issue - it is an analysis assumption about the cause.

My intention in filing #15233 was to report the bug that the edgePadding parameter is persisted. That’s an issue in and of itself, not just a supposed cause of another issue. (A setter’s auxiliary parameter should never have a lasting side effect. We can be sure that the edge padding in -setCamera:withDuration:animationTimingFunction:edgePadding:completionHandler: is auxiliary because “with” appears before it in the method signature.)

[pozdnyakov]

Hi, neither 1st nor 2nd suggestions work. I can't apply your #15308 patch on my 5.3.0 branch there is too many conficts from the master branch.
I don't know how to help you more.

@RomainQuidet Hi, do you have any updates on the issue? #15308 has landed, is it feasible for you to try out current master branch?

[RomainQuidet]

Hi, I was able to take some time to merge the master on our branch, unfortunately the infinite loop is still there, using 110+% of CPU.
I'll try to make some more logs in to help out to find what's going on.

@pozdnyakov after further investigations, I was not able to reproduce the issue on a sample but our production app.
In this app, on a navigation mapView, we quickly set the user tracking (done by setting a camera and updating the mapView) and update the mapView insets. Combination of both lead to a dead loop.
If I remove either user tracking or insets update, the mapView behave correctly.
So branch iOS 5.1+ introduced a strange bug here.

[venkatchm]

Hi,
We are also experiencing the same issue in our app.
Here is the screenshot from Xcode Energy Organiser.
Mapbox version 5.2.0.

[chloekraw]

@venkatchm - thanks for the report. do you have the same implementation as others in this thread?

if not: in 5.4.0, we published a PR (#15308) as well as other performance improvements (e.g. #15600) that are intended to alleviate this problem. would you mind testing out 5.4.0 and seeing if you can reproduce the same problem?

@RomainQuidet - thanks for the information, sorry to hear that your issue isn't fully resolved, we'll keep digging and we appreciate the help.

[pozdnyakov]

@RomainQuidet it's hard to guess the exact reason just from the screen shot, however #15086 could be a speculative fix, in case the problem is caused with infinite loop of the map update inside a transition handler. Could you pls try it out?

[RomainQuidet]

Hi I tried the 5.4.0 release and had the same incorrect behavior (not an manual map usage but during Gps session). The cpu usage is too high and the app can’t update correctly. I’ll try your patch as soon as possible. Romain

…

Le 22 oct. 2019 à 14:11, Mikhail Pozdnyakov ***@***.***> a écrit :  @RomainQuidet it's hard to guess the exact reason just from the screen shot, however #15086 could be a speculative fix, in case the problem is caused with infinite loop of the map update inside a transition handler. Could you pls try it out? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

[astojilj]

@RomainQuidet

In this app, on a navigation mapView, we quickly set the user tracking (done by setting a camera and updating the mapView) and update the mapView insets.

Could you please share the code for this - values used for insets and tracking before and after. Are both called from callbacks? How frequent the change of values happens?

on a navigation mapView

Do you use navigation SDK here?

Combination of both lead to a dead loop.
If I remove either user tracking or insets update, the mapView behave correctly.

Do you still see updateFromDisplayLink called all the time?

Thanks.

[astojilj]

@venkatchm,

In this app, on a navigation mapView, we quickly set the user tracking (done by setting a camera and updating the mapView) and update the mapView insets.

Is your code also doing this?

[venkatchm]

@astojilj We are not using navigation mapView. We render custom layers (MGLLineStyleLayer, MGLSymbolStyleLayer ) on the Map and we set the setVisibleCoordinateBounds based on predefined coordinate.

@chloekraw We see this issue in the 5.4.0 SDK. Here are the screenshots of Xcode Energy Organiser

[astojilj]

@astojilj We are not using navigation mapView. We render custom layers (MGLLineStyleLayer, MGLSymbolStyleLayer ) on the Map and we set the setVisibleCoordinateBounds based on predefined coordinate.

@chloekraw We see this issue in the 5.4.0 SDK. Here are the screenshots of Xcode Energy Organiser

@venkatchm I am especially interested if there is tilt/pitch set, if edgePadding is supplied to setVisibleCoordinateBounds and if large top contentInset is used. Thanks.

[astojilj]

@JustinGanzer,
Thank you for the reproduction code. Using this code, it was easy to reproduce it in 5.1. As I am not able to reproduce it with the latest master branch, let's close the issue and identify any further performance problems as separate issues here.

To verify it, Swift code from original report is ported to ObjC and used in iosapp (it was convenient way for me to reproduce and debug it):

diff --git a/platform/ios/app/MBXViewController.m b/platform/ios/app/MBXViewController.m
index 82a68e074..e144d4ccc 100644
--- a/platform/ios/app/MBXViewController.m
+++ b/platform/ios/app/MBXViewController.m
@@ -1553,6 +1553,26 @@ - (void)addLatLonGrid
                                                                                source:source];
     labelLayer.text = [NSExpression expressionForKeyPath:@"value"];
     [self.mapView.style addLayer:labelLayer];
+
+    source = [[MGLComputedShapeSource alloc] initWithIdentifier:@"pictures" options:nil];
+    UIImage *blueBoxImage = [self imageWithText:@"XY" backgroundColor:[UIColor blueColor]];
+    [self.mapView.style setImage:blueBoxImage forName: @"picture"];
+
+    MGLSymbolStyleLayer *layer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"pictures" source:source];
+    layer.iconAllowsOverlap = [NSExpression expressionForConstantValue:@YES];
+    layer.minimumZoomLevel = 6.0;
+    NSString *nameOfPictures = @"picture";
+    NSString *matching = [NSString stringWithFormat:@"'%@', '%@'", nameOfPictures, nameOfPictures];
+    NSString *formatImageName = [NSString stringWithFormat:@"MGL_MATCH(highlight, %@, '%@')", matching, nameOfPictures];
+    NSExpression *functionImage = [NSExpression expressionWithFormat:formatImageName];
+    layer.iconImageName = functionImage;
+    layer.keepsIconUpright = [NSExpression expressionForConstantValue:@YES];
+
+    NSDictionary *scaleStops = @{@6: @0.3, @11: @0.6, @14: @0.88};
+    layer.iconScale = [NSExpression expressionWithFormat: @"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1, %@)", scaleStops];
+
+    [self.mapView.style addSource:source];
+    [self.mapView.style addLayer:layer];
 }
 
 - (NSString *)bestLanguageForUser

When using 5.1 release branch code, the issue is reproducible - with no interaction with the map, GPU consumption is high all the time:

When using the latest master, this looks resolved.

@RomainQuidet, @venkatchm,

There is a chance that the issue you are facing is not related to the issue here: it is about constant GPU re-rendering and high GPU energy consumption (green boxes at the diagram), even there is no user interaction.

Once you stop interaction with the map, does it still has high CPU/GPU usage like it was in initial report?

if not, we would likely need to address the other issues as a new one and provide further information needed to reproduce them. The fact that you see the same code in trace is just about the fact that it is the hottest code path and it is expected - we need to figure out why it is triggered more than expected.

Could you please provide more details about the style and layers your map has? If you could share this and some code, it would help us focusing on the problem. Thanks.

[JustinGanzer]

@astojilj Funny coincidence but I had just tested the newest release on various devices from ios 12.0 all the way to 13.2 with xcode 11 and 11.2. The problem appears resolved as I can not reproduce the issue in the test controller provided in my original issue message, neither in our production app. Great job!

I have however noticed a much much higher cpu usage now than before when applying a custom contentInset to the MGLMapView and animating the camera. I only mention this since you have expressed interest about it to venkatchm.

I'll open a new issue once I've managed to create a reproduce-able instance of it.

[astojilj]

@JustinGanzer,
Thanks for help. Related to contentInset, I needed to verify it is not related to this: #15163. It is not.