Thanks to:
Michael Matthews <matthewm_at_voyager.sgate.com>
Alan Davis <davis_at_decatl.alf.dec.com>
Paul Henderson <pgh_at_unx.dec.com>
Dr. Tom Blinn <tpb_at_zk3.dec.com>
Sheryl A. Campbell <campbell_at_lvc.edu>
Thanks for the advice, everyone agreed that sysconfigtab and
dxkerneltuner was the way to go vs rebuilding the kernel. I will post my
original question at the end. But I really wanted to include Alan, Tom and
Paul's remarks because they all were points well taken and I can't really
summarize what they said:
-------------------------------------------------------------------------
Alan Davis <davis_at_decatl.alf.dec.com>:
Karen,
As development continues on dynamic kernel tuning, more
and more of what used to be "kernel parameters" are moving
to "system configuration parameters". It's recommended that
any values that are configurable in /etc/sysconfigtab be set
there rather than in the kernel.
One feature of v4.0+ is the boot-time kernel load, ie building
a kernel in memory at boot time rather than loading the /vmunix
pre-built kernel. Dynamic linking of the kernel will use only
the values in /etc/sysconfigtab, not the /sys/conf/SYSNAME values.
Also, /etc/sysconfigtab values over-ride those built into the
/vmunix kernel.
-------------------------------------------------------------------------
Paul Henderson:
Karen,
I would encourage you to use dxkerneltuner to change kernel attibutes.
It is easy to use and is a lot easier to use than a dbx -k of the
kernel.
Dxkerneltuner will write the changed attribute to your system's
/etc/sysconfigtab file. If it did not, then there was some problem.
Please check that file and get back to me.
Please note that you can also use the sysconfig and sysconfigdb
commands to see/set kernel attributes. With dxkerneltuner and
sysconfig/sysconfigdb, you won't need to use dbx for the most
commonly set kernel attributes ever again.
-------------------------------------------------------------------------
Dr. Tom Blinn:
To the extent that there is a "right manual", it should be the System
Administration or System Tuning and Performance Management manual.
Where it's possible to use dxkerneltuner or a similar tool that updates
the /etc/sysconfigtab file, that's the way to go. Originally, many of
the parameters resulted in static allocation of fixed-size data structures
in the kernel, so the only way to change the sizes of the data structures
was to rebuild the kernel. Over time, especially to support scalability
of the system, we've made the data structures dynamically allocated and
sized by the values in /etc/sysconfigtab or alternatively by examining the
system to find memory size, peripheral options, and so on.
It's even a goal to get to the point where you never have to build a
static kernel for the system -- where the needed pieces are loaded
dynamically at boot time, and all the data structures are dynamically
allocated. We aren't 100% there yet.
So, the PREFERRED mechanism is to use the /etc/sysconfigtab file and those
utilities that modify it. Over time, it's a goal to have EVERYTHING done
dynamically from the parameters in that file. The fact that you can still
use the parameters in the system configuration file and set up sizes is an
artifact of the old way, and preserving it for people who don't read the
f*
manuals :^)
-------------------------------------------------------------------------
My original question:
>Managers,
>
> We have 2 new machines both running 4.0B. I've recently had to
>tune some kernel parameters on these machines and ran into a different
>method of doing this than I used to do it before. For example, on our
>older machine, when I had to change maxusers, I did the whole kernel
>rebuild thing. Now, I've used the dxkerneltuner (same as the sysconfigtab
>file way) and just rebooted. I've checked the configuration file and it
>wasn't updated. But, when I checked the maxusers parameter using dbx, it
>was changed.
>
> My questions are - What's the better way to do it? Does it in fact
>do the same thing except for having the value in the config file? Does
one
>override the other if there was a different value in the config than
there
>was in the sysconfigtab file?
>
> The manuals on these only really talk about what they do - but
>does not compare the two - saying which ones the best way to do it.
>(unless I haven't read the right manual that is)
------------------------------------------------------------------------------
Karen Thomas
Connecticut State University System Office
Information System
THOMASK_at_CTSTATEU.EDU
PHONE: (860) 493-0118
Received on Wed Mar 26 1997 - 21:35:12 NZST