On Mon, Feb 23, 2009 at 10:14:24AM +0000, Colin Guthrie wrote: > 'Twas brillig, and Lennart Poettering at 23/02/09 02:05 did gyre and gimble: >> OpenSUSE apparently does not enable it. The same is true for >> Ubuntu. Same for Debian. Note sure about Mandriva. > > Here is a (not quite current) grep from my running kernel (it's .27 as > .28/.29 both break my intel graphics :( at the moment): > > $ zgrep -E "HZ|PREEMP" /proc/config.gz > CONFIG_PREEMPT_NOTIFIERS=y > CONFIG_NO_HZ=y > # CONFIG_PREEMPT_NONE is not set > CONFIG_PREEMPT_VOLUNTARY=y > # CONFIG_PREEMPT is not set > # CONFIG_HZ_100 is not set > # CONFIG_HZ_250 is not set > # CONFIG_HZ_300 is not set > CONFIG_HZ_1000=y > CONFIG_HZ=1000 > CONFIG_MACHZ_WDT=m > > I'll ask our kernel team why PREEMPT is not on as I've no idea of the > consequences. My guess is that it relates to graphics drivers... Debians kernel doesn't have PREEMPT and _HZ_1000, because there is some fear that this might be bad for performance on server loads (lower throughput because of more context switches). I've poked them about this again last week and it's on their TODO list to have a good look at what the actual consequences of the config changes would be. If someone has links to good benchmarks comparing performance of recent kernel with various combinations of _HZ and _PREEMPT options that would be very usefull Sjoerd -- Don't stop to stomp ants when the elephants are stampeding.
