David Aurelio e7499e39a4 limit number of workers
Summary:This limits the number of spawned transformation workers depending on the number of available cores (`n`):

```
n < 3   → n
n < 8   → floor(3/4 * n)
n < 24  → floor(3/8 * n + 3) // factor going from 3/4 to 1/2
n >= 24 → floor(n / 2)
```

Reviewed By: bestander

Differential Revision: D2999894

fb-gh-sync-id: 0163240b5f066432f9ba07161c0dfa2ec767ba58
shipit-source-id: 0163240b5f066432f9ba07161c0dfa2ec767ba58
2016-03-02 07:31:42 -08:00
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2016-03-02 07:31:42 -08:00