From owner-freebsd-doc Sat Jun 16 16: 0:49 2001 Delivered-To: freebsd-doc@freebsd.org Received: from freefall.freebsd.org (freefall.freebsd.org [216.136.204.21]) by hub.freebsd.org (Postfix) with ESMTP id C0CC337B40D for ; Sat, 16 Jun 2001 16:00:18 -0700 (PDT) (envelope-from gnats@FreeBSD.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.11.3/8.11.3) id f5GN0IH90724; Sat, 16 Jun 2001 16:00:18 -0700 (PDT) (envelope-from gnats) Date: Sat, 16 Jun 2001 16:00:18 -0700 (PDT) Message-Id: <200106162300.f5GN0IH90724@freefall.freebsd.org> To: freebsd-doc@freebsd.org Cc: From: Dima Dorfman Subject: Re: docs/27599: md(4) manpage enhancement Reply-To: Dima Dorfman Sender: owner-freebsd-doc@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org The following reply was made to PR docs/27599; it has been noted by GNATS. From: Dima Dorfman To: Stefan `Sec` Zehl Cc: FreeBSD-gnats-submit@freebsd.org Subject: Re: docs/27599: md(4) manpage enhancement Date: Sat, 16 Jun 2001 15:52:52 -0700 Stefan `Sec` Zehl writes: > On Wed, May 23, 2001 at 08:57:23PM -0700, Dima Dorfman wrote: > > sec@ice.42.org writes: > > > --- /usr/export/src/share/man/man4/md.4 Sun Dec 31 03:11:56 2000 > > > +++ ./md.4 Thu May 24 00:56:57 2001 > > > @@ -59,6 +59,11 @@ > > > with the kernel option > > > .Dv MD_NSECT . > > > .Pp > > > +Be warned that due to kernel constraints such a > > > +.Nm > > > +disk cannot be bigger than a certain maximum size. > > > +This size can be found in the 'Limit' column of 'vmstat -m'. > > > +.Pp > > > > It looks to me like the man page already states this: > > > > The default maximum size of a md disk backed by malloc(9) is 20,000 se > c- > > tors of 512 bytes each. This can be changed with the kernel option > > MD_NSECT. > > > > Perhaps it might make sense to mention vmstat(8), but I don't think > > it's appropriate to add another paragraph, most of which just repeats > > what has already been said. > > I'm sorry, but you misunderstand. The problem I mention has nothing to > do with MD_NSECT. You can raise MD_NSECT all the way, but the mentioned > 'Limit' column of 'vmstat -m' Is unaffected by that. That is exactly > where this comes from. The default MD_NSECT is small enough to avoid any > problems, but when you increase it, you run into that other, not yet > documented limit which will HANG your machine. > If my english isn't clear enough, feel free to improve it. But please > add a warning to the manpage. Okay, I did misunderstand. But it still says what you want: The malloc(9) backed disks are severely limited in size by constraints imposed by malloc(9). The limit imposed depends on the amount of physi- cal RAM in the machine, and covers all malloc(9) backed instances of md devices. but perhaps that could do with some elaboraton. How about this: The malloc(9) backed disks are severely limited in size by constraints imposed by malloc(9). Specifically, only one malloc bucket s used, which means that all md devices with malloc(9) backing must share the malloc per-bucket quota. The exact size of this quota varies, in particuar with the amount of RAM in the system. The exact value can be determined with vmstat(8). > > CU, > Sec > -- > There are too many priorities. One has to prioritize priorities. -- Wietse > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-doc" in the body of the message