From owner-dev-commits-src-main@freebsd.org Fri Jun 18 14:43:48 2021 Return-Path: Delivered-To: dev-commits-src-main@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id E8C56646C35; Fri, 18 Jun 2021 14:43:48 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4G61rh62TQz4jcg; Fri, 18 Jun 2021 14:43:48 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id B7E2924A09; Fri, 18 Jun 2021 14:43:48 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 15IEhmFd010712; Fri, 18 Jun 2021 14:43:48 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 15IEhm3h010711; Fri, 18 Jun 2021 14:43:48 GMT (envelope-from git) Date: Fri, 18 Jun 2021 14:43:48 GMT Message-Id: <202106181443.15IEhm3h010711@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Warner Losh Subject: git: 0f882bb14a0e - main - NOTES: Update the HZ entry with latest advice. MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: imp X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 0f882bb14a0e772bf901b1a3e40d028a4165fbd9 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for the main branch of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Jun 2021 14:43:49 -0000 The branch main has been updated by imp: URL: https://cgit.FreeBSD.org/src/commit/?id=0f882bb14a0e772bf901b1a3e40d028a4165fbd9 commit 0f882bb14a0e772bf901b1a3e40d028a4165fbd9 Author: Warner Losh AuthorDate: 2021-06-18 14:39:18 +0000 Commit: Warner Losh 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 +# kernel timeouts. With the adaptive tick code, lower values produce less +# benefit than in the past. options HZ=100