performance issue with SetTag in Activity with large number of tags

[jaeyoon21]

I looked into source of Activity. I realized that Tag is maintained as LinkedList and every SetTag calls lock() and iterates the all tags to check if there is same key or not.
In our case, we have lots of tags, so locking and iterate LinkedLIst for every setTag might be performance issue.

1. Can we have SetTag (using Map) instead of LinkedList
2. Can we have SetTag without locking? (in some case, application owner/programmer know that Activity is not called across multiple threads. So no locking is safe.

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Issue Details

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I looked into source of Activity. I realized that Tag is maintained as LinkedList and every SetTag calls lock() and iterates the all tags to check if there is same key or not.
In our case, we have lots of tags, so locking and iterate LinkedLIst for every setTag might be performance issue.

1. Can we have SetTag (using Map) instead of LinkedList
2. Can we have SetTag without locking? (in some case, application owner/programmer know that Activity is not called across multiple threads. So no locking is safe.

Author:	jaeyoon21
Assignees:	-
Labels:	tenet-performance, untriaged, area-System.Diagnostics.Activity
Milestone:	-

[cijothomas]

SetTag is designed to be thread-safe, so locking(or equivalent) mechanism is required and hence, simple Dictionary cannot be used as a replacement! (ConcurrentDictionary could be, but that won't be much better in terms of perf for small number of tags (which is the common case). Might help to run benchmarks with diff. scenarios to see if any alternate datastructure might help.

The deduplication check could be expensive, and would be nice to get a opt-in feature to remove deduping logic.