Date: Fri, 18 Jun 2021 17:14:15 +0200 From: Gary Jennejohn <gljennjohn@gmail.com> To: Warner Losh <imp@FreeBSD.org> Cc: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: 0f882bb14a0e - main - NOTES: Update the HZ entry with latest advice. Message-ID: <20210618151415.6c28e706@ernst.home> In-Reply-To: <202106181443.15IEhm3h010711@gitrepo.freebsd.org> References: <202106181443.15IEhm3h010711@gitrepo.freebsd.org>
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On Fri, 18 Jun 2021 14:43:48 GMT Warner Losh <imp@FreeBSD.org> wrote: > The branch main has been updated by imp: > > URL: https://cgit.FreeBSD.org/src/commit/?id=0f882bb14a0e772bf901b1a3e40d028a4165fbd9 > > commit 0f882bb14a0e772bf901b1a3e40d028a4165fbd9 > Author: Warner Losh <imp@FreeBSD.org> > AuthorDate: 2021-06-18 14:39:18 +0000 > Commit: Warner Losh <imp@FreeBSD.org> > CommitDate: 2021-06-18 14:41:56 +0000 > > NOTES: Update the HZ entry with latest advice. > > Sponsored by: Netflix > Differential Revision: https://reviews.freebsd.org/D30804 > --- > sys/conf/NOTES | 16 ++++++---------- > 1 file changed, 6 insertions(+), 10 deletions(-) > > diff --git a/sys/conf/NOTES b/sys/conf/NOTES > index 40063c09382f..89dd572986bc 100644 > --- a/sys/conf/NOTES > +++ b/sys/conf/NOTES > @@ -1047,8 +1047,7 @@ options TCP_SIGNATURE #include support for RFC 2385 > > # DUMMYNET enables the "dummynet" bandwidth limiter. You need IPFIREWALL > # as well. See dummynet(4) and ipfw(8) for more info. When you run > -# DUMMYNET it is advisable to also have at least "options HZ=1000" to achieve > -# a smooth scheduling of the traffic. > +# DUMMYNET, HZ/kern.hz should be at least 1000 for adequate response. > options DUMMYNET > > # The DEBUGNET option enables a basic debug/panic-time networking API. It > @@ -1237,14 +1236,11 @@ options CAPABILITY_MODE # sandboxes with no global namespace access > ##################################################################### > # CLOCK OPTIONS > > -# The granularity of operation is controlled by the kernel option HZ whose > -# default value (1000 on most architectures) means a granularity of 1ms > -# (1s/HZ). Historically, the default was 100, but finer granularity is > -# required for DUMMYNET and other systems on modern hardware. There are > -# reasonable arguments that HZ should, in fact, be 100 still; consider, > -# that reducing the granularity too much might cause excessive overhead in > -# clock interrupt processing, potentially causing ticks to be missed and thus > -# actually reducing the accuracy of operation. > +# The granularity of operation is controlled by the kernel option HZ (default > +# 1000 or 1ms). Virtual machines guests default to an HZ value of 100. Lower > +# values produce less overhead at the expense of reduce accuracy in delivery of reduce should be reduced > +# kernel timeouts. With the adaptive tick code, lower values produce less > +# benefit than in the past. > > options HZ=100 > > _______________________________________________ > dev-commits-src-all@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/dev-commits-src-all > To unsubscribe, send any mail to "dev-commits-src-all-unsubscribe@freebsd.org" -- Gary Jennejohn
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