Cap the amount of text copied into the stringbuilder in JsonRpcEventSource.Format#1187
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AArnott merged 1 commit intomicrosoft:mainfrom May 7, 2025
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…ource.Format Speedometer test shows two LOH allocations occurring in this method when opening a large cs file, when the value passed into the method is a JsonDocument. 1) The ToString call on the document 2) pushing the results of the ToString call into the StringBuilder It would be non-trivial to get rid of the first allocation, however, the second can be removed by just calling the StringBuilder.AppendOverload that takes in a range from the given string to copy into the StringBuilder.
AArnott
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May 7, 2025
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Thanks.
I don't anticipate a runtime perf benefit because this code only runs when an ETW trace is collected that specifies the streamjsonrpc ETW provider explicitly. Still, it may make our perf runs a little faster and a little more 'true' to customer perception.
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This was referenced Jan 22, 2026
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Speedometer test shows two LOH allocations occurring in this method when opening a large cs file, when the value passed into JsonRpcEventSource.Format is a JsonDocument.
It would be non-trivial to get rid of the first allocation, however, the second can be removed by just calling the StringBuilder.Append overload that takes in a range from the given string to copy into the StringBuilder.
Here's is the allocation from the speedometer test that this is attempting to improve: