smp kernels
I had noticed that my new desktop never really used 100% of the
CPU, this bothers me for a couple of reasons, first off, if I am
doing something CPU intensive like compiling bzflag, then please
use all of the CPU, that's what it is there for. If there are other
apps running, let the kernel decide how much you get.
Secondly, if you don't use as many cycles as you can get, building
takes much much longer. Bzflag used to take, on my old desktop,
about 6 mins to compile, now on the new desktop it was taking 20-30
mins. Yuck. This blog now takes about a half hour to build which is
ridiculously long. So I headed to #linux on irc.arstechnica.com to
investigate. At first the new 4GB of ram was thought to be a
culprit but removing a stick had no effect. The command
dd
if=/dev/urandom | bzip2 > /dev/null was used as a pseudo
benchmark, this command should spin up the CPU to 100% right away
but mine would sit there at 50% or so. Next I turned off
hyper-threading in the bios. This seemed to work, when I rebooted I
reran the benchmark and got 100% CPU usage right away. Problem
solved I thought. However with HT turned off the system was very
poor at multitasking, compiling something and then checking irc or
email was a chore as now my terminals kept refreshing all the
time.
Next up was to check the kernel, I had installed a stock debian
kernel,
linux-image-2.6.17-1-686, but didn't realize
it came with
SMP
enabled. I decided to try compiling a new kernel the Debian Way™ so
I installed
fakeroot debhelper modutils kernel-package
libncurses5-dev and then I did
make menuconfig
and removed the SMP support and followed that with
make-kpkg
clean and finally to actually build the kernel,
sudo
fakeroot make-kpkg --append_to_version -686 --initrd
--revision=rev. 01 kernel_image and got a cup of tea, while
I anxiously waited. The Debian Way™ is pretty nifty as it builds a
.deb that is easily installed and makes a ramdisk and updates grub
all in one shot, and can be removed like any other package.
After rebooting I rebuilt bzflag in 4 mins, a considerable
improvement. I thought I solved the problem but I had tested
things by recompiling bzflag without doing a
make
clean so after a fresh checkout it took 40 minutes to build
:( I don't know what the next move will be now, more poking around
in the kernel I suppose.
(PS thank you Sophmore and johnf in #linux for the help)
(PPS
building
kernel's the Debian way.)
UPDATE: This morning I reverted
to a 2.6.15 kernel but had the same results which led me to believe
it might not even be kernel related at all, so on a hunch I removed
2 sticks of RAM and rebooted into the 2.6.17 kernel and everything
was zippy and fast again. So it looks life 2GB of ram is the life
for me. I can use the other 2GB elsewhere I suppose but its a shame
it doesn't work with 4GB.