Mono System.Text.Json.Tests on Windows timing out

[directhex]

Description

There may be a performance regression in Mono on Windows (or the test suite has grown and we can no longer finish it in time), as we are now frequently timing out our CI in System.Text.Json.Tests

System.Text.Json.Tests, commit 6c27393: https://helix.dot.net/api/2019-06-17/jobs/2798f22e-585e-4940-a1ba-5eac77edc617/workitems/System.Text.Json.Tests

System.Text.Json.Tests, commit 3d75475: https://helix.dot.net/api/2019-06-17/jobs/fa673262-133f-4f16-baf9-0cc657cb74fc/workitems/System.Text.Json.Tests

System.Text.Json.Tests, commit 0446e4f: https://helix.dot.net/api/2019-06-17/jobs/e803feb0-ce9c-4645-b3a0-25ce0947fc37/workitems/System.Text.Json.Tests

System.Text.Json.Tests, commit 2269b06: https://helix.dot.net/api/2019-06-17/jobs/54f496ef-5f53-4d46-9169-f18480ca70c5/workitems/System.Text.Json.Tests

System.Text.Json.Tests, commit 8933510: https://helix.dot.net/api/2019-06-17/jobs/0653fec5-7b16-4d4c-9741-543f68c35dec/workitems/System.Text.Json.Tests

System.Text.Json.Tests, commit fd09c80: https://helix.dot.net/api/2019-06-17/jobs/257bbeea-72ae-4c05-8f42-6a48a4a555ce/workitems/System.Text.Json.Tests

Runfo Tracking Issue: System.Text.Json.Tests Mono Windows Failure

Build	Definition	Kind	Run Name

Build Result Summary

Day Hit Count	Week Hit Count	Month Hit Count
0	0	0

[Jacksondr5]

Commit 0446e4f did add a large outer loop test that we estimate added about 8 seconds to the inner loop test execution time (relevant PR discussion). As such, we marked it as outer loop. I can't verify how much the individual test contributes to the outer loop run since I'm having issues building on my local right now. It is worth noting that this new test is based off a test with similar structure and behavior, so I'm not sure if this commit really made a difference or not.

[jaredpar]

runfo query for this failure https://runfo.azurewebsites.net/search/tests/?bq=definition%3Aruntime+started%3A%7E7&tq=System.Text.Json.Tests

[ViktorHofer]

cc @layomia @ericstj @steveharter

[ViktorHofer]

I believe this happening on CoreClr as well: #42817

[layomia]

Just merged a PR disabling the relevant tests on Mono + Windows - #42960. Removing blocking-clean-ci label for now.

[layomia]

Linking my comment from #42960 (comment). cc @ViktorHofer