Tech Empower Fortunes System.Data perf improvements

[joshfree]

https://www.techempower.com/benchmarks/#section=data-r14&hw=ph&test=fortune

Tracking issue for :

1. (~10%) Fix system.data.sqlclient!System.Data.ProviderBase.DbConnectionPoolIdentity.GetCurrent on windows to cache the windows identity, or to mimic what Linux does
2. (~4%) There are hot locks in system.data.sqlclient
   a. (2.7%) system.data.sqlclient!System.Data.ProviderBase.DbConnectionPool.PrepareConnection
   b. (.3%) system.data.sqlclient!System.Data.SqlClient.SqlConnection+OpenAsyncRetry.Retry
   c. (.5%) system.private.corelib!System.Threading.TimerQueueTimer.Change

@vancem @mikeharder

[danmoseley]

@geleems is this still on track for 3/30?

[mikeharder]

CC: @sebastienros

[divega]

As recently announced in the .NET Blog, focus on new SqlClient features an improvements is moving to the new Microsoft.Data.SqlClient package. For this reason, we are moving this issue to the new repo at https://github.com/dotnet/SqlClient. We will still use https://github.com/dotnet/corefx to track issues on other providers like System.Data.Odbc and System.Data.OleDB, and general ADO.NET and .NET data access issues.

[Wraith2]

I investigated and proposed changes to some of these items in dotnet/corefx#37157 Ultimately it was closed because the benefits were small and only evident at startup, see the discussion for details.

The remaining item is to change PrepareConnection from locking to a RWLS which i've got a branch for but am waiting on code in this repo.

On linux identity is the hostname and this is safe because impersonation is not supported. On windows impersonation is possible and the hostname does not change when using it, so using th elinux mechanism on windows is insecure. The thing that can't be avoided is fetching the current user security identity. It might be possible to avoid some string allocations by caching the last identity seen and then comparing it to the fetched one.