Date: Wed, 21 Jan 2004 13:25:42 +0100 From: Uwe Doering <gemini@geminix.org> To: freebsd-stable@freebsd.org Subject: Re: Where are defaults for kernel variables? Message-ID: <400E6FC6.6010801@geminix.org> In-Reply-To: <xzp65f5o7lf.fsf@dwp.des.no> References: <20040120132533.GA24163@neuron.tuke.sk> <400E3628.8050601@geminix.org> <xzp65f5o7lf.fsf@dwp.des.no>
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Dag-Erling Smørgrav wrote:
> Uwe Doering <gemini@geminix.org> writes:
>>Jozef Babjak wrote:
>>>options PMAP_SHPGPERPROC=201
>>>or options KVA_PAGES=260
>>>but are these default values?
>>
>>No, these are usually not the defaults, just examples. I haven't
>>found a complete list so far. I could be wrong, but I think part of
>>the problem is that the majority of kernel developers doesn't feel
>>obligated to document the variables they introduced somewhere outside
>>the kernel.
>
> The defaults are generally computed at boot time as a function of
> physical memory size.
While there are a number of variables that get derived from the physical
memory size (if not overridden), claiming that kernel variable defaults
are _generally_ computed at boot time is certainly an exaggeration.
There are still tons of variables and C preprocessor defines that have
nothing to do with physical memory size, have fixed defaults and have to
be set explicitly where necessary. And many of those are unfortunately
sparsely documented, if at all.
Now, before someone gets me wrong on this, I don't complain about the
lack of documentation, since the FreeBSD project is a voluntary effort
and I don't have the time to solve this problem, either. I just
describe the current state of affairs, as I see it.
Uwe
--
Uwe Doering | EscapeBox - Managed On-Demand UNIX Servers
gemini@geminix.org | http://www.escapebox.net
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