Date: Thu, 17 Jun 2021 10:11:23 -0600 From: Warner Losh <wlosh@bsdimp.com> To: Gary Jennejohn <gljennjohn@gmail.com> Cc: Alexey Dokuchaev <danfe@freebsd.org>, Warner Losh <imp@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 0a99422970d7 - main - Move mips and arm to 1000Hz by default. Message-ID: <64D62F0A-A7CA-4D4F-92E8-D4FF173F7870@bsdimp.com> In-Reply-To: <20210617093111.5a537750@ernst.home> References: <202106170201.15H215Z6078742@gitrepo.freebsd.org> <YMsT7mfByZa5765c@FreeBSD.org> <20210617093111.5a537750@ernst.home>
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--Apple-Mail=_B90A1E55-6D79-490D-9D72-C146A3F586B5 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On Jun 17, 2021, at 3:31 AM, Gary Jennejohn <gljennjohn@gmail.com> = wrote: >=20 > On Thu, 17 Jun 2021 09:20:46 +0000 > Alexey Dokuchaev <danfe@freebsd.org> wrote: >=20 >> On Thu, Jun 17, 2021 at 02:01:05AM +0000, Warner Losh wrote: >>> commit 0a99422970d7fbdb1e17724339a8dc37082f3431 >>>=20 >>> Move mips and arm to 1000Hz by default. >>>=20 >>> armv6 and armv7 systems already were 1000Hz. The other armv5 were = a >>> mix of 100 and 1000. This changes them to 1000. Should there be >>> issues, we can add options HZ=3D100 to the systems that have bad >>> performance at the drop of a hat. >>=20 >> Do we have this 1000Hz vs. 100Hz thing documented somewhere for those >> who are thinking about tuning it? There are various "optimization" >> howto's floating on the Internet here and there which recommend this >> change, so it would be nice to have some definitive documentation on >> the subject, e.g. in our Handbook or Wiki. >>=20 >=20 > It's discussed in /sys/conf/NOTES, but most users probably wouldn't > think about looking there. An entry in the Handbook or Wiki could > be useful. I=E2=80=99ve brought over NetBSD=E2=80=99s hz(9) and hardclock(9) man = pages in https://reviews.freebsd.org/D30802 with adjustments for = FreeBSD. I mention the kern.hz tunable and the fact that it default to = 100 for VM guests. This should cover people=E2=80=99s curiosity as well = as plug the hole in our docs. All this stuff was from 4.4BSD, so = NetBSD=E2=80=99s man pages were a good place to start. The HZ kernel option is something almost nobody should be adjusting. = I=E2=80=99ve updated the text slightly in NOTES in = https://reviews.freebsd.org/D30804 if people want to tweak it further = before I commit. Wiki is terrible for this stuff, since it goes stale = too quickly, but I=E2=80=99d be happy to review someone else=E2=80=99s = changes to the handbook for tuning this value (though honestly, it = should almost never be frobbed). kern.hz likely shouldn=E2=80=99t be = adjusted either, but it=E2=80=99s a much easier knob to turn than = rebuilding the kernel with a new HZ and there=E2=80=99s more cases where = it can be useful (though tests I=E2=80=99ve done in the past suggest = values > 10,000-50,000 might not be that useful). Finally, NetBSD has an option(4). We=E2=80=99re long past the time where = we should consider it. I=E2=80=99d love to review changes for that too. = Most of a first cut on text can be stolen from NOTES, if someone is = looking for an easy project (it need not be complete to be useful, at = least initially) Warner --Apple-Mail=_B90A1E55-6D79-490D-9D72-C146A3F586B5 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIzBAEBCgAdFiEEIDX4lLAKo898zeG3bBzRKH2wEQAFAmDLdCsACgkQbBzRKH2w EQDsRhAAzi5FLrUlwBp1+CEsizCnUR2YSlycuvEwX5szj1QXYE7WLxiSyYPWWLFR 5OtSRCUJnCH+hF17g+A9FAlR9zEefOcc9qqhAsKELH7zLZFzhCT+3PtYrHPp5oY4 WSlR55vmJJvHCyenrFN/jY4XqsLMLeuwJFXx8ZgzPYr/YUJ5O/nmOMXfSnotGCjm rOQNBMX4ig2618KgLn0yQfvkQDyUt/vn/yEMiOJu+6qZ+tipANHq7dWscDAODEkv gwktkyZP3kFW3e06Rl9td846FMwNxS7kthJLfIXcJ6fzFBTMQcCM9SIwg36mj2UZ lrI6JKW0oIVEVQ88AHBayTb4a7zTLZWfgOXVRMZmWZu8IriW+ch7fs/INCvNlGzT CAjvIb/j21LJnmPXuOp9RJAPCNIA4Kp+7fOuD+aQBHNi8j0Mfg8o3OerQRHpnTMk Cokh57YeGcq3Y/MeWil+c74CCUJA3xBWQ0ALIAtjIINuCkGgmgn1wBzdZMO1F1y9 tD1WQrAYZ5NIgvcAAmRjJwYj+1s2acs0Lr9yNwkZXjKgVzCvf2J6AGms19JXduBc zFE7j9VKXq+3QqUfTO2fbaOasi9h+ovaajBuHVo9K7FyErSKgGAsh/8sC8N8+2jD 1uqMXkmMjaYvwVQ4X21eX8Dv+PoP1CnjS9JUCLn+dmc92BJ2eDM= =ymi/ -----END PGP SIGNATURE----- --Apple-Mail=_B90A1E55-6D79-490D-9D72-C146A3F586B5--
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