Date: Wed, 27 Jun 2018 12:36:42 -0400 From: Jung-uk Kim <jkim@FreeBSD.org> To: Andriy Gapon <avg@FreeBSD.org>, FreeBSD Current <freebsd-current@FreeBSD.org> Subject: Re: TSC calibration in virtual machines Message-ID: <4d7957f6-9497-19ff-4dbb-436bb6b05a56@FreeBSD.org> In-Reply-To: <8ac353c5-d188-f432-aab1-86f4ca5fd295@FreeBSD.org> References: <8ac353c5-d188-f432-aab1-86f4ca5fd295@FreeBSD.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --i3db1n5AU0SP87SkKIjI4GhC9VJU1zR7S Content-Type: multipart/mixed; boundary="DE1LZOkh9kxFql1fzPsgzKkQJkdJC3Vej"; protected-headers="v1" From: Jung-uk Kim <jkim@FreeBSD.org> To: Andriy Gapon <avg@FreeBSD.org>, FreeBSD Current <freebsd-current@FreeBSD.org> Message-ID: <4d7957f6-9497-19ff-4dbb-436bb6b05a56@FreeBSD.org> Subject: Re: TSC calibration in virtual machines References: <8ac353c5-d188-f432-aab1-86f4ca5fd295@FreeBSD.org> In-Reply-To: <8ac353c5-d188-f432-aab1-86f4ca5fd295@FreeBSD.org> --DE1LZOkh9kxFql1fzPsgzKkQJkdJC3Vej Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 06/27/2018 03:14, Andriy Gapon wrote: >=20 > It seems that TSC calibration in virtual machines sometimes can do more= harm > than good. Should we default to trusting the information provided by a= hypervisor? >=20 > Specifically, I am observing a problem on GCE instances where calibrate= d TSC > frequency is about 10% lower than advertised frequency. And apparently= the > advertised frequency is the right one. >=20 > I found this thread with similar reports and a variety of workarounds f= rom > administratively disabling the calibration to switching to a different = timecounter: > https://lists.freebsd.org/pipermail/freebsd-cloud/2017-January/000080.h= tml We already do that for VMware hosts since r221214. https://svnweb.freebsd.org/changeset/base/221214 We should do the same for each hypervisor. Jung-uk Kim --DE1LZOkh9kxFql1fzPsgzKkQJkdJC3Vej-- --i3db1n5AU0SP87SkKIjI4GhC9VJU1zR7S Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEl1bqgKaRyqfWXu/CfJ+WJvzb8UYFAlszvSAACgkQfJ+WJvzb 8UYU2Af+Ou3jz23pGMgvsQ4gUbdS2znHEvu7mD/z70iyKwg8+MHivYR7dw06yLzn VKPHsttg/TyJFcRqi60U1kIMzJkdbngiQ65bxwzm/TCAeLIbFWaxga/tYwfBvroP 9pTBq1G7wghktAXYpDWRVlNeKdrLx595auOTU/BRiLlV72q8aU7SxnqZkNACmvna rff3USaZa8OVWo/YfFLH2PdZlT5+rpgkP1b4gR/wWoZLjQy87Ko+dNrMTrqNKe9T 3SyHj3tJJsUs/X1Zi9YMD2C7s7AdTXKLJ1RuL4bN1TkF4v3pUltO5ZjK45Sm/pvH KLJ6ySjth5xhW06RNqMiQgPQu75veQ== =oUJ2 -----END PGP SIGNATURE----- --i3db1n5AU0SP87SkKIjI4GhC9VJU1zR7S--
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