Date: Mon, 12 Jun 2006 16:32:48 -0400 From: Kris Kennaway <kris@obsecurity.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: Scott Long <scottl@samsco.org>, danial_thom@yahoo.com, freebsd-performance@freebsd.org Subject: Re: Initial 6.1 questions Message-ID: <20060612203248.GA72885@xor.obsecurity.org> In-Reply-To: <20060612210723.K26068@fledge.watson.org> References: <20060612195754.72452.qmail@web33306.mail.mud.yahoo.com> <448DC818.9070100@samsco.org> <20060612210723.K26068@fledge.watson.org>
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--mYCpIKhGyMATD0i+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 12, 2006 at 09:08:12PM +0100, Robert Watson wrote: > On Mon, 12 Jun 2006, Scott Long wrote: >=20 > >I run a number of high-load production systems that do a lot of network= =20 > >and filesystem activity, all with HZ set to 100. It has also been shown= =20 > >in the past that certain things in the network area where not fixed to= =20 > >deal with a high HZ value, so it's possible that it's even more=20 > >stable/reliable with an HZ value of 100. > > > >My personal opinion is that HZ should gop back down to 100 in 7-CURRENT= =20 > >immediately, and only be incremented back up when/if it's proven to be t= he=20 > >right thing to do. And, I say that as someone who (errantly) pushed for= =20 > >the increase to 1000 several years ago. >=20 > I think it's probably a good idea to do it sooner rather than later. It= =20 > may slightly negatively impact some services that rely on frequent timers= =20 > to do things like retransmit timing and the like. But I haven't done any= =20 > measurements. As you know, but for the benefit of the list, restoring HZ=3D100 is often an important performance tweak on SMP systems with many CPUs because of all the sched_lock activity from statclock/hardclock, which scales with HZ and NCPUS. Kris --mYCpIKhGyMATD0i+ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (FreeBSD) iD8DBQFEjc9wWry0BWjoQKURAoX7AKD3jrbSgbmpMEQibSGwucYvLxt9aACg3Y/i 5SbAlN+kIKUkkGdkZ3genJs= =+GDa -----END PGP SIGNATURE----- --mYCpIKhGyMATD0i+--
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