Illumos 4881

Illumos 4881 - zfs send performance regression with embedded data
    
4881 zfs send performance degradation when embedded block pointers are encountered
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Ported by: Tim Chase <tim@chase2k.com>