CODEWITHSUNDEEP
c#multithreading
morteza khosravi
morteza khosravi

Reputation: 1619

ThreadLocal and Task

I use a static ThreadLocal to cache some heavyweight objects. Consider the following code:

class MatchItemFinder
{
    private static ThreadLocal<PaddedImage> tempImage;
    MatchItemFinder()
    {
        if(tempImage==null) 
            tempImage = new ThreadLocal<PaddedImage>(
            () => new PaddedImage(patchSize, patchSize));
    }
    internal void DoSomething(){
        //Do something with tempImage.Value
    }
}

When DoSomething() is called from multiple Task Parallel Library threads, when each instance is created? I mean obviously threads are reused so is my tempImage created every time a thread is created or every time a thread is reused?

With a design perspective do you think this kind of caching would be a great decision or there are better strategies to cache large objects in a thread safe manner?

I'm using .Net 4.

Upvotes: 0

Views: 580

Answers (1)

usr
usr

Reputation: 171236

Thread local variables do not cooperate with the TPL or with the thread pool. They are Thread-based. When any TPL library function reuses a thread your thread locals will be reused.

With a design perspective do you think this kind of caching would be a great decision or there are better strategies to cache large objects in a thread safe manner?

If your cache items are immutable there is no need for thread local items. Use a global cache.

Upvotes: 2

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