Reminder from years back: we would love to have a Haifux talk about timers, time, tickless kernel, Jiffies, etc. So if you (that's you) are reading this, and are interested in the topic, what is a better time to learn it to depth and talk about it?
Thanks Orna On Wed, Jul 25, 2012 at 3:28 PM, Oleg Goldshmidt <[email protected]> wrote: > > > On Wed, Jul 25, 2012 at 2:29 PM, Nadav Har'El <[email protected]>wrote: > >> >> HZ used to default to 100 in the Linux kernel, but now it actually >> defaults (unless I'm mis-remembering) to 250, and this is where the 4-ms >> resolution came from. > > > Actually, there is the default HZ and inside the kernel HZ there is HZ > that you can configure at compile time (with CONFIG_HZ) and USER_HZ, which, > I think, is still 100 whether or not the kernel's HZ is customized. I think > USER_HZ is what is important for "soft timers" you are interested in. > > Unless you configure the kernel yourself, the HZ value the kernel comes > with probably depends on the distro. The tradeoff is as follows: desktop > systems benefit from a higher HZ value because interactive processes are > latency-sensitive. Servers, especially NUMA systems, don't have interactive > processes and may, on the other hand, experience a lot of unpleasant > effects (bus contention as an example) if there are lots of interrupts. > Also note that the interrupt rate will be HZ*#CPUs. > > I am used to RedHat systems whose kernels normally come with HZ=100. You > are talking about a server as well, right? You may be right about HZ=250 by > default in the vanilla kernel that is supposed to be a compromise between > 100 and 1000. > > If you go back to, say, 2.6.11 or 2.6.12, then you'll see HZ=1000 by > default, I think. Was that "Linux on a desktop"? ;-) > > > -- > Oleg Goldshmidt | [email protected] > > _______________________________________________ > Linux-il mailing list > [email protected] > http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il > > -- Orna Agmon Ben-Yehuda. http://ladypine.org
_______________________________________________ Linux-il mailing list [email protected] http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
