1909 disk sync write perf regression when slog is used post oi_148 Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: Eric Schrock <eric.schrock@delphix.com> Reviewed by: Robert Mustacchi <rm@joyent.com> Reviewed by: Bill Pijewski <wdp@joyent.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Reviewed by: Steve Gonczi <gonczi@comcast.net> Reviewed by: Garrett D'Amore <garrett.damore@gmail.com> Reviewed by: Dan McDonald <danmcd@nexenta.com> Reviewed by: Albert Lee <trisk@nexenta.com> Approved by: Eric Schrock <eric.schrock@delphix.com>