bge(4) sysctl tuneables -- a blast from the past. more knobs! MORE!

[Sean Bruno]

Version 0.2 of patches to bge(4).  I'm not totally happy with it, but
comments welcome.  I need better explanations of usage for the man page.

I've dropped bge_rxd completely here as it was suggested to not even
bother adjusting it.

http://people.freebsd.org/~sbruno/bge_config_update_1.txt


> I didn't notice before that these are tunables and not sysctls.  That's
> much more broken.  Actually tuning using them like I do with sysctls
> would take ~10000 reboots.  Tunables are bogus for anything that isn't
> needed for booting.  Optimizations are needed for booting.
> 

Done and changed.  Things seem to do the right thing when adjusted.

> Technical bugs include:
> - wrong defaults are claimed for *coal_ticks.  The defaults are 150, but
>    are claimed to be 150 milliseconds.  These values are dimensionless,
>    but since ticks take 1 microsecond each, 150 gives 150 microseconds,
>    not 150 milliseconds.
man page updated to reflect usec timing.  checked the tech docs as well
and confirmed microseconds.

> - *coal_bds is claimed to be a count of packes (sic).  Actually, it is a
>    count of buffer descriptors.  Small packets take 1 bd, but normal
>    packets take 2, and jumbo packets many (?).  The best tuning may be
>    depend on the average bds/packet.
man page updated with wording that attempts to say this.

> - the new tunables are in the wrong namespace (hw instead of dev)
fixed

> - the new tunables are too global (bge instead of bge.N)
fixed

> 
> There are only 2 bge tunables now, and they only have half of these bugs:
> - hw.bge.allow_asf is in the wrong namespace
> - hw.bge.allow_asf is too global
Maintainer disagrees with this.

> - dev.bge.%d.msi seems to be correct.
> Both of the old tunables are needed for boot-time configuration.
> 
> Bruce


Sean
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