MEF加载插件效率如何？插件并行实例化能力咨询

Hey there! Let's break down your questions about MEF and plugin performance clearly:

1. Does MEF natively handle plugin loading/instantiation in parallel? #

Short answer: No, out-of-the-box MEF doesn’t automatically parallelize plugin instantiation.

The default CompositionContainer operates synchronously—when you call methods like GetExportedValues<T>(), it discovers, loads, and instantiates each plugin one after another. That means with your 5-25 plugins (each taking 1-10 seconds to initialize), you’d end up with a total load time equal to the sum of all initialization durations (worst case: 250 seconds) if you stick to MEF’s default behavior.

But you absolutely can add parallelism on top of MEF’s API with minimal extra code. Here’s a practical approach:

• First, fetch Export<T> objects instead of fully instantiated plugins using GetExports<T>(). This gives you references to the plugins without triggering initialization right away.
• Use Task.WhenAll() to parallelize the instantiation step by accessing each Export<T>’s Value property in a separate task.

Example code snippet:

// Grab exports without instantiating them immediately
var pluginExports = container.GetExports<IPlugin>();

// Parallelize the initialization work
var initializedPlugins = await Task.WhenAll(
    pluginExports.Select(export => Task.Run(() => export.Value))
);

2. Performance impact when replacing your custom system with MEF #

How MEF stacks up against your custom solution depends on how your current system operates:

• If your custom system already uses parallel instantiation: Switching to default MEF will slow down startup (since it’s synchronous). But once you add the parallel logic above, performance should match or even exceed your custom system—MEF is optimized for plugin management, so you won’t lose much (if any) efficiency.
• If your custom system is synchronous: MEF’s performance will be on par or slightly better in most cases. It’s a mature, battle-tested framework, so it avoids the unoptimized edge cases or rough spots common in custom plugin loaders.

The biggest win with MEF is reduced maintenance: you’ll ditch the need to keep updating custom plugin discovery, dependency resolution, and lifecycle code. That’s a massive long-term benefit, even if you need to write a small amount of parallelism logic upfront.

Final Recommendation #

If parallel startup is non-negotiable, plan to implement the parallel instantiation pattern with MEF as shown. Test with your actual plugin set to confirm performance matches your custom system. For most teams, the tradeoff between less maintenance and minor parallelism code is well worth making.

内容的提问来源于stack exchange，提问作者Michael