.net 7 cycles Performance slow

[quan0zhou]

Description

    public class BenchmarkSum
    {
        private JsonObject[] _jsonObjs;


        [GlobalSetup]
        public void Setup()
        {
            _jsonObjs = new JsonObject[100000];
        }

        [Benchmark]
        public void Sum()
        {
            for (int i = 0; i < 100000; i++)
            {
                _jsonObjs[i] = new JsonObject()
                {
                    ["aaa"] = 1,
                    ["bbbb"] = 2,
                    ["cccc"] = new JsonArray()
                    {
                        new JsonObject()
                        {
                            ["aaaa"] = "aaaaa",
                            ["ffffff"] = "ffffffffffffff"
                        }
                    }
                };
            }
        }
    }

Configuration

Regression?

Data

Analysis

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[stephentoub]

@eiriktsarpalis, @krwq, here's an allocation trace with the repro but for only 1,000 iterations instead of 100,000 iterations. On the left is .NET 6, on the right is .NET 7:

That's a lot of additional allocation. Is this expected?

[eiriktsarpalis]

Superficially, this appears to only be creating DOM instances without performing any serializations, so I'm surprised that any JsonSerializerOptions instance are materialized. Would need to take a closer look.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

    public class BenchmarkSum
    {
        private JsonObject[] _jsonObjs;


        [GlobalSetup]
        public void Setup()
        {
            _jsonObjs = new JsonObject[100000];
        }

        [Benchmark]
        public void Sum()
        {
            for (int i = 0; i < 100000; i++)
            {
                _jsonObjs[i] = new JsonObject()
                {
                    ["aaa"] = 1,
                    ["bbbb"] = 2,
                    ["cccc"] = new JsonArray()
                    {
                        new JsonObject()
                        {
                            ["aaaa"] = "aaaaa",
                            ["ffffff"] = "ffffffffffffff"
                        }
                    }
                };
            }
        }
    }

Configuration

Regression?

Data

Analysis

Author:	quan0zhou
Assignees:	-
Labels:	area-System.Text.Json, tenet-performance
Milestone:	-

[stephentoub]

@eiriktsarpalis, I assume the intent was for this to be static?!

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonNode.To.cs

Line 9 in a5f3676

private protected readonly JsonSerializerOptions s_defaultOptions = new();