Red Hat Bugzilla – Bug 54176
[performance/VM] Slow application startup
Last modified: 2007-04-18 12:37:25 EDT
Graphical applications are slow to start on a K6-2/400 running kernel-2.4.9-0.5. By comparison, starting gedit, emacs or gnumeric is almost instantaneous on the same box running FreeBSD 4.4. I have 384MB of RAM, so this isn't a thrashing issue -- things are slow even when launching cached applications and no swap is being used. The performance problem could be in glibc and not the kernel. I don't know enough to say for sure.
Be advised that the 2.4.9-0.5 kernel has quite a few debugging options enabled, such as slab poison. Comparisons with production compiled kernels is hence dangerous....
Mea culpa. I'll build the latest -ac with a non-debug config and try again.
Ok, tested with 2.4.9-0.5custom and debug options off. Subjectively, it does seem faster than with debugging on, but it's still quite a bit slower than FreeBSD. I'm going to do some more profiling on both platforms and report back here.
Does typing echo 511 > /proc/sys/vm/max-readahead help ?
It made a slight difference, but over ten runs it was small enough that I don't think it's statistically significant.
Closing bug -- user error. Too much RAM on a cheap motherboard favors FreeBSD, as Linux allocates memory top-to-bottom and winds up running out of uncached memory.