kernel configuration

Don don at calis.blacksun.org
Wed Mar 31 07:32:24 PST 2004


> o According to LINT the CONF_FLAGS "inhibit use of non-optimal function"
> does this mean that my kernel will be "optimized"?
If you don't know what a kernel variable or flag does, then don't use it.
FreeBSD performs really well without configuring every last option.

> o I increased the process limits to MAXDSIZ="(1024 * 1024 * 1024)" and
> DFLDSIZ="(1024 * 1024 * 1024)". For an old PC like mine, is this a good
> idea? I mostly use my computer for programming. However, I'd also like
> it to be quite responsive at times. Any ideas?
>
> o PQ_CACHESIZE, what is it? what difference does it make if i set it to 512 and not 256?
Don't bother setting either of these options. The defaults that the kernel
uses are based on your available memory and are good starting points.

> o The options like: CPU_BLUE_LIGHTNING, CPU_ENABLE_SSE,
> CPU_FASTER_5x86_FPU, CPU_SUSP_HLT, NO_FOOF_HACK. Are they all
> applicable to my CPU?
No.

>
> o USER_LDT, what is this? is it good or bad?
This allows user level control of the LDT (Local descriptor table or some
such). This is needed by some programs.

> o options like: KTRACE, INVARIANTS, INVARIANT_SUPPORT, DIAGNOSTIC are
> for kernel debugging, am I right? I also read in LINT that it will make
> my kernel size larger. Does large kernels means worse performance? Do I
> really need to debug my kernel?
It will make a slightly larger kernel and it will be slightly slower.
Disable these options unless you intend on doing debugging.

> o PERFMON, do I need it? does it improve performance?
Up to you. Not directly.

> o UCONSOLE, USERCONFIG & VISUAL_USERCONFIG, do i need them? I'll be
> running X, and according to handbook, UCONSOLE is good for something.
> What about the rest? Why do they have comments like "XXX - don't belong
> here" in LINT. Are they not suppose to be used?
UCONSOLE allows the user to grab the console. The other two options are
unnecessary.

Most of these options are described on the web or in the FreeBSD handbook.

-Don


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