Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request, I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

avoid sendFile() for ranges or object lengths < 4MiB

Motivation and Context

SendFile() has a tiny overhead for smaller streams

How to test this PR?

It is more challenging to test on laptops; the results are

* Average:  6.07% ( 1077.3 MiB/s) throughput,  6.07% ( 269.3) obj/s

There is a consistent number here.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here