How much RAM is needed for FreeBSD

[Greg 'groggy' Lehey]

[Format recovered--see http://www.lemis.com/email/email-format.html]

Incorrect quotation

On Saturday,  5 April 2003 at 14:33:37 -0600, Alfonso Romero wrote:
> On  Saturday, April 05, 2003 10:23 AM, Clemens Jaeger wrote:
>>
>> I was looking for information : how much RAM is needed to run FreeBSD on
>> a Pentium Computer?
>> There is no information on your website / documentation for Version 5.0
>
> well, but if you try to use GNOME... with 32MB it took my Pentium
> 133Mhz PC 30 minutes to load the environment!

You certainly shouldn't be running memory-hungry suites like GNOME or
KDE on systems with minimal memory.

On Saturday,  5 April 2003 at 11:41:59 -0800, Kent Stewart wrote:
> On Sunday 06 April 2003 12:06 pm, kitsune wrote:
>> On Sat, 5 Apr 2003 12:59:23 -0500, Matthew Emmerton wrote:
>>>> On Sat, 05 Apr 2003 18:23:18 +0200
>>>> Clemens Jaeger wrote:
>>>>> I was looking for information : how much RAM is needed to run
>>>>> FreeBSD on a Pentium Computer?  There is no information on your
>>>>> website / documentation for Version 5.0
>>>>
>>>> should be something like 4Mb, iirc
>>>
>>> *cough*.  You haven't tried to install FreeBSD since the 2.2.x days
>>> then :)
>>>
>>> My recommendation is no less than 16MB.

I think this is a valid minimum.  We're pretty sure that we can no
longer install in 8 MB.  It's possible that it would work in 12 MB,
but where do you find systems with that amount of memory?

>> What was it like back then?

It was generally possible in 4 MB in those days.  We've seen cases of
really trimmed kernels booting in 2 MB.

>> Yeah, 16 works nicely, which is the smallest amount of ram I've
>> ever had in a machine I installed FreeBSD on.

For some definition of "nicely".  Don't expect a ball of flame.

> I think numbers like this border on meaningless. They are basically
> what you need to just run the system.

Well, sure, but that has a meaning.  There are a number of
applications, notably in networking, which don't need much more than
minimum memory.  As I observed above, you're not going to run X with a
bloatware desktop on it.  Expect to use at least 64 MB for that.

> If you want to use it for something real, then you need more. How
> much more depnds on what you want to do.  For example, to use
> X-Windows, you need 50-64MB just for X.

You can run X in 32 MB.  You need *much* more memory for
Microsoft-like programs such as newer "desktops" and OpenOffice.

I did some research on this while writing the relevant chapters for
the fourth edition of "The Complete FreeBSD", which should be out soon
(http://www.oreilly.com/catalog/cfreebsd/index.html).  I had intended
to describe only KDE or GNOME.  After seeing how much memory they used
and how little advantage you get from it, I added the alternative of
fvwm2.  It's not as easy to configure, but it runs in about 5% of the
memory footprint, and it gives you just about all the functionality.

> If you want to do a buildworld, you need Y MBs.

Building the world is relatively easy on the system.

> You need Y MB to run an application.

For some other definition of Y?

> If you want to do all of the above at the same time, then you have
> to assign values to Y and add what is appropriate together. I think
> the smallest machine that I used and didn't see a lot of swapping
> was 128 MB. Swapping drops your effective memory speed from 8ns to 8
> ms. 

Well, not quite.  You get a page of instructions each time you swap.

Greg
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