I am experiencing an enormous memory leak in my WPF project and am trying to figure out what I can do to minimize it. To access resources I use StaticResource 100% of the time. Should I use DynamicResource where I can? Are there advantages as far as memory management between StaticResource and DynamicResource?
FYI: I have a listbox showing data via a DataTemplate. As the user scrolls up/down memory increases fast, reaching 1GB in just a couple of minutes of scrolling up/down.
This is unlikely to be a StaticResource / DynamicResource thing. Static and dynamic refer to lookup strategies, not retention strategies:
StaticResource means "look up the
resource once, then just keep using
the same value."
DynamicResource means "look up the
resource each time it's needed, in
case the value has changed."
What you are doing therefore sounds correct: use StaticResource for unchanging resources such as DataTemplates (and reserve DynamicResource for resources that may change, such as system brushes that might change if the user changes the system colour scheme). The allocation of the DataTemplate via the StaticResource reference will cost no more memory than allocating it via a DynamicResource reference, and long term will be cheaper because WPF doesn't have to keep going back and re-evaluating the reference.
What is more likely is that your template itself is doing something which, when the template is applied (instantiated on a data item), is allocating memory (or indirectly causing memory to be allocated) in a leaky way. One counterintuitive cause that I've seen for this is if the template uses old-style bitmap effects. Another is if the template invokes code-behind that hooks up event handlers. But neither of these is likely to be affected by the way you reference the template resource.
As far as I know the client's operating system is very important.
WPF is designed to work for Vista and later systems (Windows 7). You may have performance problems with xp users.
Related
In perhaps a case of newbie overreach, I'm building a complex control (using WPF C#. see pic) in which automatic garbage collection does not seem to do as well as it could: I can get better memory use if I force a manual gc. I'm not sure if I should worry about it.
The ListView displaying "SectionList" is using a fair bit of memory (perhaps 100MB), as one would expect with all those controls. It's a ListView bound to an ObservableCollection of "sections" (e.g. "Math 125") (typically around 50 or so) a property of a semester object. If I dynamically change the semester to another with similar content (thus binding the listview to a different observable collection of sections) I notice memory usage going up by about 100MB, even after some auto garbage collection. It doesn't seem to be a memory leak, as if I manually force gc I can more or less recover the 100MB.
I've experimented with various virtualization options on the listview e.g. setting IsVirtualizing=true/false, using recycling mode etc. Nothing seems to make much of a difference. There seems to be way more garbage available for pickup than the automatic collector sees and disposes. I know there's garbage there because a manual gc.Collect() collects it. All in all if I force gc from time to time I can keep memory usage of the whole app at around 300MB, but not if I don't.
The question is what might be going on here that the garbage pickup is being missed?
(Or do I completely misunderstand the issues at hand here?)
I can get better memory use if I force a manual gc. I'm not sure if I should worry about it...It doesn't seem to be a memory leak, as if I manually force gc I can more or less recover the 100MB.
If you don't have a memory leak somwhere in your code, you have nothing to worry about really.
This is the nature of nondeterministic garbage collection, i.e. you don't know and you cannot control when the GC returns memory to the operating system. As long as you don't introduce memory leaks that prevent the GC from doing its job propertly, you should be fine.
If memory usage is a hard requirement or if object lifetime may cause side effects in your application, using a managed runtime such as .NET is probably not the best option after all.
Working with WinForms you have to free memory after using gdi objects, event handlers, objects from native code, etc.
In WinForms I used to remove for example event handlers in the dispose method.
What is the best workaround to prevent memory leaks in Wpf? Is it the same as in Winforms using Dispose pattern? At all, do I have to care about event handlers, gdi objects in Wpf? What about the runtime created resources(Brushes, etc)?
This blog post lists the most common situations that cause memory leaks in WPF applications.
Event handlers to objects in parent windows
Registering to events from static objects
Using timers
Data binding
Changing the Text property of a text box
It also describes how to fix these common issues.
Another good approach is to develop an app while following the standard guidelines and then use some kind of profiler to determine any memory leaks or performance bottlenecks.
From MSDN: Any WPF framework-level element (those objects deriving from either FrameworkElement or FrameworkContentElement) has three common lifetime events: Initialized, Loaded, and Unloaded.
.....
Unloaded is raised last and is initiated by either the presentation source or the visual parent being removed. When Unloaded is raised and handled, the element that is the event source parent (as determined by Parent property) or any given element upwards in the logical or visual trees may have already been unset, meaning that data binding, resource references, and styles may not be set to their normal or last known run-time value.
Some helpful links on WPF resource dictionary leaks:
DynamicResource\StaticResource cause memory leaks
Memory leak problem with ResourceDictionary and MergedDictionaries
Watch out for events: it's very easy to miss something, because all references from the delegate will exist until the delegate lives. I suggest to use weak event pattern when it's possible. Actually Microsoft uses it in their Prism framework.
http://msdn.microsoft.com/en-us/library/aa970850.aspx
Also check out an issue that I was catched by many times when learning WPF http://support.microsoft.com/kb/938416/en-us
My control is being kept alive because of command it is bound to. How can I break this reference? This is causing a major memory leak in my application. The control is inside of a DataTemplate so I have no direct access to it.
Here is my ANTS memory profile:
How on earth do I break this connection?
Though I incorporated WeakEventListener, I discovered that my problem was with the control I was using to wrap up my images. I was hooking it up to DownloadProgress, ImageOpened, and ImageFailed events and never unhooked them. My thinking was that nothing else in my code was touching the BitmapImage objects so they would be garbage collected with the control. This, it sees, is not the case. The BitmapImage objects were referenced by a static member (and therefore a GC root) deep within Microsoft's code called "ManagedPeerTable.PeggedManagedPeersWithRefs". It was so deep that a Google search returned only five results for it. Now I suppose there will be six.
Is there any chance that memory leak can occur by using Dependency property binding or Styles. It is showing weak reference in Memory profiling tool and if i remove the binding or style weak reference is not there?. Any idea what will be the cause of that memory leak?
Not that I have ever detected. And I've used WPF to build some pretty complex 3D UI's.
Weak References are kept until the system needs to garbage collect the location. It is an optimization issue, not a memory leak. The usage of weak references mean that the coder thinks that an object is nice to have around (i.e. sort of cached), but is also OK not to have around (can reload it). So it is up to the .NET runtime to decide when to reclaim a weak-referenced object.
Quite a few WPF constructs are implemented using weak references (I believe triggers and stuff).
If you need to access a WPF control from the code behind, you need to supply a Name attribute to it in XAML.
In many cases, you don't need to access controls from the code behind, since a lot of coding logic such as binding is better applied directly inside XAML.
My question is: Is there a performance gain from not supplying the name attribute to controls? Or is it a good habit to give names to all controls on the page?
Yes there is definitely a performance gain from not supplying "name" attributes.
WPF's "Name" mechanism can be useful, but it uses extra RAM and CPU in several ways:
The XAML compiler allocates an extra slot in your class for every named object (4 bytes each)
The XAML compiler adds code to your class to initate each of these
The BAML processor calls back your code to initialize the name in each case
The BAML processor also adds the name to a dictionary, requiring an additional 20+ bytes per name
When looking up names you really need you may run into dictionary collisions with names you don't really need
For a simple control, adding a Name to control can increase the cost of using that control by 5% or so. That's not a lot, but why waste your CPU cycles and your RAM on names that are unnecessary?
Bottom line: If you don't need Names on your objects, don't name them. Usually the content or binding of a control is plenty to identify a control's purpose. And if that isn't enough documentation, you can always use XML comments, which are free.
I'd have to say it is a very bad habit to name all your controls, not just because of the cost but also because it encourages you to refer to your controls by name rather than using proper view model and binding techniques. Most of my XAML doesn't use "Name" for any controls, let alone all of them.