Kernel configuration options

[Albert Cahalan]

[various people]

> BSD process accounting and auditd support though?

BSD process accounting can be very useful for debugging.
It is particularly valuable when you have programs being
started from weird places, being debugged already, or
crossing through stuff like setuid. It doesn't cost much.

I suspect the auditd support may likewise prove useful.

> CONFIG_PROFILING, CONFIG_KPROBES, CONFIG_DEBUG_FS,
> CONFIG_UNUSED_SYMBOLS, CONFIG_SCHEDSTATS, CONFIG_TIMER_STATS,
> CONFIG_DEBUG_PREEMPT, CONFIG_DEBUG_SPINLOCK

We need CONFIG_PROFILING for sure. Unless the overhead is
high, I'd keep the rest.

> Finally, I'm noticing a lot of stuff can be built as modules,
> but is built in.  Networking in its entirety; sound drivers;
> mouse; and USB (the mouse looks like it's PS2)

I have a strong reason to want modular libertas: bug #46.

I suggest avoiding any situation where multiple modules need
to be loaded. (one depends on another)

> In the current dyntick scheme the regular clock interrupt still
> happens when the processor is busy - it's only disabled when
> things go idle.  So you still need to set HZ to something.
> It also sets the resolution of much of the timekeeping within
> the kernel.

Since there are no clock ticks when idle, you may as well go
with 1000. It's better for music and video.

>>> I'd keep the debug symbols (which shouldn't cost any memory
>>> at runtime).
>> Possibly not.  The kernel runs inside one giant huge page doesn't it?
>> 4MiB read-write-execute...
>
> Not on the Geode: we don't have MTRRs, so I guess the kernel
> is being mapped by 4KB pages.

The main kernel runs in 4 MB or 2 MB pages on any system with
the MMU capabilities of the Pentium. This works on the Geode.
It has nothing to do with MTRRs, which are used to control the
cache attributes. Kernel modules reside in regular 4 KB pages.

Those debug symbols are required so that "ps -el" can tell you
where a process is stuck. Better:

ps -emostat,wchan:22,pid,tid,pcpu,comm,args

Also, do not remove hugetlbfs. One could use that for speed
in programs that deal with big arrays. I've actually seen the
difference in a performance class I took. It can really matter.