[PATCH 1 of 2 V4] perf: omit copying ui and redirect to ferr if buffer API is in use

[Yuya Nishihara]

On Wed, 16 Nov 2016 10:28:07 +0100, Philippe Pepiot wrote:
> # HG changeset patch
> # User Philippe Pepiot <philippe.pepiot at logilab.fr>
> # Date 1479222657 -3600
> #      Tue Nov 15 16:10:57 2016 +0100
> # Node ID ab6e50ddc2c56dcf170991293005be6d6f80a232
> # Parent  e1d6aa0e4c3aed73e0dc523b8a8fd5f9fe23510a
> perf: omit copying ui and redirect to ferr if buffer API is in use

Queued the series per the last reviews. Thanks for both writing and reviewing
this.