Buffer writes from sources of synchronous writes

[pranavkm]

Fixes #6397

[pranavkm]

Based on https://github.com/aspnet/AspNetCore/blob/master/src/Mvc/Mvc.ViewFeatures/src/Buffers/PagedCharBuffer.cs#L78-L97 without some of the ceremony

[pranavkm]

Before and after on the MVC Json scenario in Benchmarks (forgot to markdown):

RequestsPerSecond:           176,013
Max CPU (%):                 99
WorkingSet (MB):             193
Avg. Latency (ms):           1.6
Startup (ms):                381
First Request (ms):          223.58
Latency (ms):                0.86
Total Requests:              2,653,337
Duration: (ms)               15,070

RequestsPerSecond:           172,219
Max CPU (%):                 99
WorkingSet (MB):             192
Avg. Latency (ms):           1.67
Startup (ms):                452
First Request (ms):          303.34
Latency (ms):                0.71
Total Requests:              2,600,366
Duration: (ms)               15,100

[pranavkm]

🆙 📅

[pranavkm]

🆙 📅

[pranavkm]

@aspnet/build any idea what's up with the Windows build failure? I'm seeing it on all my PRs and I couldn't see a issue tracking it.

[dougbu]

@pranavkm see #9477 which is @natemcmaster's work to address this issue.