Messages in this thread | | | Date | Mon, 28 Jul 2003 17:38:16 -0400 (EDT) | From | Bill Davidsen <> | Subject | Re: [patch] sched-2.6.0-test1-G6, interactivity changes |
| |
On Mon, 28 Jul 2003, Ingo Molnar wrote:
> > On Mon, 28 Jul 2003, Con Kolivas wrote: > > > On Sun, 27 Jul 2003 23:40, Ingo Molnar wrote: > > > - further increase timeslice granularity > > > > For a while now I've been running a 1000Hz 2.4 O(1) kernel tree that > > uses timeslice granularity set to MIN_TIMESLICE which has stark > > smoothness improvements in X. I've avoided promoting this idea because > > of the theoretical drop in throughput this might cause. I've not been > > able to see any detriment in my basic testing of this small granularity, > > so I was curious to see what you throught was a reasonable lower limit? > > it's a hard question. The 25 msecs in -G6 is probably too low.
It would seem to me that the lower limit for a given CPU is a function of CPU speed and cache size. One reason for longer slices is to preserve the cache, but the real time to get good use from the cache is not a constant, and you just can't pick any one number which won't be too short on a slow cpu or unproductively long on a fast CPU. Hyperthreading shrinks the effective cache size as well, but certainly not by 2:1 or anything nice.
Perhaps this should be a tunable set by a bit of hardware discovery at boot and diddled at your own risk. Sure one factor in why people can't agree on HZ and all to get best results.
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |