Peformance issues with r278325

[John Baldwin]

On Friday, March 18, 2016 12:01:37 PM Stanislav Sedov wrote:
> 
> > On Mar 18, 2016, at 11:16 AM, Stanislav Sedov <stas at freebsd.org> wrote:
> > 
> > FWIW we are currently testing the delay '1' change.  Unfortunately, the test is
> > not easy to repeat (we didn't find a synthetic one yet that results in the same
> > outcome), so it does take more time that I would like.  Will follow up with the 
> > results.
> > 
> > We did try HEAD as well a while ago, and although it exhibited the same pattern.
> > However it did not utilize the x2apic unfortunately, as it does seem to be disables
> > in the BIOS (FreeBSD reports it being disables in the DMAR table).
> > 
> > Thanks for looking into it!
> > 
> 
> Replying to my own message.
> 
> The `delay 1` test was a success, we were not able to reproduce the same issues
> as we had with a 5us delay in that loop.  So perhaps we should commit the delay
> change into stable/10 instead of reverting the code altogether (I assume the original
> change was done to solve a real issue?).

Ok, I will commit this to HEAD today.  Thanks!

-- 
John Baldwin