.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

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.

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();