[AVRO-3893] Significant allocations from unnecessary lambda capture on deserialization path

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: csharp
• Labels: c# pull-request-available

Language

C#

• Assignee: Unassigned
• Reporter: Jannick Bitsch
• Created: 24/Oct/23 07:11
• Updated: 24/Oct/23 08:33

Description

During investigation of a GC issue in a C# project we discovered that ~10% of allocations could be attributed to an unnecessary lambda capture on a hot-path of Avro deserialization while utilizing a PreresolvingDatumReader. 

 

The capture happens in ObjectCreator.FindType where, instead of using the 'key' parameter passed to the value function, the lambda captures the 'name' method parameter:

 

private Type FindType(string name)
{
    return typeCacheByName.GetOrAdd(name, (_) =>
    {
        Type type = null;

        if (TryGetIListItemTypeName(name, out var itemTypeName))
        {
            return GenericIListType.MakeGenericType(FindType(itemTypeName));
        }

        if (TryGetNullableItemTypeName(name, out itemTypeName))
        {
            return GenericNullableType.MakeGenericType(FindType(itemTypeName));
        }

        ....
 

It should be a simple improvement to use the value passed to the Func<string, Type> instead. Will open a PR. 

Issue Links

• links to: GitHub Pull Request #2565