Messages in this thread | | | Date | Tue, 5 Jan 1999 21:25:25 -0800 (PST) | From | "B. James Phillippe" <> | Subject | Re: [PATCH] HZ change for ix86 |
| |
On Tue, 5 Jan 1999, Kurt Garloff wrote:
> Hey guys, > > lately, I've seen a couple of questions about changing HZ in the kernel for > ix86. Your scheduler will run more often and your system might feel snappier > when increasing HZ, that's why we want it. Overhead for doing so got > relativlely low with recent CPUs, so me might really want it. ... > I created a patch which changes the values of HZ to 400 and fixed all places > I could spot which report the jiffies value to userspace. I think I caught > all of them. Note that 400 is a nice value, because we have to divide the > values by 4 then, which the gcc optimizes to shift operations, which can be > done in one or two cycles each and even parallelized on modern CPUs. Integer > divisions are slow on the ix86 (~20 cycles) and the sys_times() needs four of
I don't know anything about it (and my box is an Alpha for which HZ is 1024), but, one ignorant proposal: would it perhaps be worthwhile to have the HZ value higher for faster (x86) systems based on the target picked in make config? Say, your 400 for Pentium+ and 100 for 486 or lower..?
cheers, -bp -- B. James Phillippe . bryan@terran.org Linux Engineer/Admin . http://www.terran.org/~bryan Member since 1.1.59 . finger:bryan@earth.terran.org
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |