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Subject: Re: Peformance issues with r278325
From: Stanislav Sedov <stas@FreeBSD.org>
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Date: Fri, 18 Mar 2016 12:01:37 -0700
Cc: Adrian Chadd <adrian.chadd@gmail.com>,
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> On Mar 18, 2016, at 11:16 AM, Stanislav Sedov <stas@freebsd.org> =
wrote:
>=20
> 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=20
> results.
>=20
> 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).
>=20
> Thanks for looking into it!
>=20

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?).

--
Stanislav Sedov
ST4096-RIPE