[PLUG] RH 8.0 Kernel Compiling
Karl M. Hegbloom
karlheg at pdxlinux.org
Fri Nov 22 05:54:47 UTC 2002
On Thu, 2002-11-21 at 19:39, Richard Steffens wrote:
> In the last several days, I have installed RH 8.0 on three machines from
> RH supplied installation CD's (the 3 CD set, not the 2 CD evaluation
> set). The first machine is a 200 Mhz MMX Pentium, the second, a 550 Mhz
> AMD K6, and the third an IBM Thinkpad 390X with a 400 Mhz Celeron. The
> first two machines have 64 Mb of RAM, each, and the laptop has 96 Mb.
>
> The installation went smoothly on all three machines. I am now
> interested in addressing performance problems on the first two machines.
> The laptop doesn't seem to have any performance problems that show up to
> my eye. On the 200 Mhz Pentium, things seem to work as expected with the
> exception of mpg123, which I reported a couple of days ago. On the 550
> Mhz AMD, the entire feel of the system is slow, feeling even slower than
> the 200 Mhz Pentium.
For playing MP3's, you might like to try "xmms", make it SUID root, and
check off the "use realtime priority" option. See if that makes it work
a little better. It is safe to make "xmms" setuid to root, since it
drops permissions very early, right after setting it's scheduling
priority to realtime round robin. (A quick look at the source code will
verify that.)
> I'm assuming that the solution is optimizing the kernel for each
> machine. I understand from replies to an earlier post that I need to
> read up on the low latency patch, and have done some of that.
The performance problems might have more to do with disk I/O latency
than anything else. Install and read about the "hdparm" tool. You can
use it to improve disk performance by quite a lot. Turn on 32bit I/O,
and DMA, and set multi count to 16. That alone will often give you
another several megabytes per second throughput. If you've got UDMA 33
or 66 hard drive + controller, but the BIOS does not set the disks into
that mode automaticly, then you can also use "hdparm" to set the UDMA
mode. It only works when the hardware can do it though.
> Today's question is, where do I start reading about what options to
> specify (or however it's done) to get a kernel that works well with the
> AMD K6 chip as opposed to the Pentium chip.
There's a checkoff in the kernel configuration (make menuconfig) for
what type of CPU you have. If you are running blazingly new Debian
unstable ("Sid"), you could try to use the "apt-build" tool to install
all your software, and have it autobuild each package with full per-CPU
optimizations. I've not tried to do this yet myself, so don't know how
well it works.
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