RELENG_10 performance regression (was Re: 35-40% performance drop releng9 vs releng10 openvpn

[Miroslav Lachman]

Mike Tancsa wrote on 03/20/2015 22:02:
> OK, I think I found where the RELENG_10 performance loss happened. It seems
> https://lists.freebsd.org/pipermail/svn-src-stable-10/2015-March/004778.html
>
> is the issue.
>
> Testing with a kernel from r279796 I get 76-77Mb of throughput.  With
> r279848 it drops to about 60Mb

I am surprised by this huge performance drop.
If it is really caused by this change (VFS timestamp precision from 
seconds to microseconds), wasn't this change tested before commit?

Miroslav Lachman