From owner-svn-src-head@freebsd.org Fri Dec 29 20:00:20 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 6052BEADA95; Fri, 29 Dec 2017 20:00:20 +0000 (UTC) (envelope-from ian@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2AC6479346; Fri, 29 Dec 2017 20:00:20 +0000 (UTC) (envelope-from ian@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id vBTK0JMK093745; Fri, 29 Dec 2017 20:00:19 GMT (envelope-from ian@FreeBSD.org) Received: (from ian@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id vBTK0JGd093744; Fri, 29 Dec 2017 20:00:19 GMT (envelope-from ian@FreeBSD.org) Message-Id: <201712292000.vBTK0JGd093744@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: ian set sender to ian@FreeBSD.org using -f From: Ian Lepore Date: Fri, 29 Dec 2017 20:00:19 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r327356 - head/share/man/man4 X-SVN-Group: head X-SVN-Commit-Author: ian X-SVN-Commit-Paths: head/share/man/man4 X-SVN-Commit-Revision: 327356 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 29 Dec 2017 20:00:20 -0000 Author: ian Date: Fri Dec 29 20:00:19 2017 New Revision: 327356 URL: https://svnweb.freebsd.org/changeset/base/327356 Log: Correct a mistake and reword a couple sentences to clarify that "the value" refers to the scale value, not the kmem_arena size that results from scaling. Suggested by: alc@ Modified: head/share/man/man4/md.4 Modified: head/share/man/man4/md.4 ============================================================================== --- head/share/man/man4/md.4 Fri Dec 29 19:07:50 2017 (r327355) +++ head/share/man/man4/md.4 Fri Dec 29 20:00:19 2017 (r327356) @@ -116,19 +116,19 @@ The default value is 32, which is sufficient to map 12 .It Cd options VM_KMEM_SIZE_SCALE= This configures the amount of kernel virtual address (KVA) space to dedicate to the kmem_arena map. -The value is the ratio of physical to virtual pages. +The scale value is the ratio of physical to virtual pages. The default value of 3 allocates a page of KVA for each 3 pages of physical ram in the system. The kernel and modules, including the root image, also consume KVA. The combination of a large root image and the default scaling -may preallocate so much KVA to kmem_arena that there is not enough +may preallocate so much KVA that there is not enough remaining address space to allocate kernel stacks, IO buffers, and other resources that are not part of kmem_arena. Overallocating kmem_arena space is likely to manifest as failure to launch userland processes with "cannot allocate kernel stack" messages. -Setting the value too high may result in kernel failure to allocate +Setting the scale value too high may result in kernel failure to allocate memory because kmem_arena is too small, and the failure may require significant runtime to manifest. Empirically, a value of 5 works well for a 200 MiB root image on