Date: Sat, 16 Jun 2001 16:00:18 -0700 (PDT) From: Dima Dorfman <dima@unixfreak.org> To: freebsd-doc@freebsd.org Subject: Re: docs/27599: md(4) manpage enhancement Message-ID: <200106162300.f5GN0IH90724@freefall.freebsd.org>
index | next in thread | raw e-mail
The following reply was made to PR docs/27599; it has been noted by GNATS.
From: Dima Dorfman <dima@unixfreak.org>
To: Stefan `Sec` Zehl <sec@42.org>
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 <sec@42.org> 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
home |
help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200106162300.f5GN0IH90724>