Messages in this thread | | | Date | Fri, 11 Jan 2002 22:42:27 +0100 | From | François Cami <> | Subject | Re: [patch] O(1) scheduler, -G1, 2.5.2-pre10, 2.4.17 (fwd) |
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Ingo Molnar wrote:
> On Thu, 10 Jan 2002, Mike Kravetz wrote: > > >>If I run 3 cpu-hog tasks on a 2 CPU system, then 1 task will get an >>entire CPU while the other 2 tasks share the other CPU (easily >>verified by a simple test program). On previous versions of the >>scheduler 'balancing' this load was achieved by the global nature of >>time slices. No task was given a new time slice until the time slices >>of all runnable tasks had expired. In the current scheduler, the >>decision to replenish time slices is made at a local (pre-CPU) level. >>I assume the load balancing code should take care of the above >>workload? OR is this the behavior we desire? [...] >> > > Arguably this is the most extreme situation - every other distribution > (2:3, 3:4) is much less problematic. Will this cause problems? We could > make the fairness-balancer more 'sharp' so that it will oscillate the > length of the two runqueues at a slow pace, but it's still caching loss. > > >>We certainly have optimal cache use. >> > > indeed. The question is, should we migrate processes around just to get > 100% fairness in 'top' output? The (implicit) cost of a task migration > (caused by the destruction & rebuilding of cache state) can be 10 > milliseconds easily on a system with big caches. > > Ingo
I do vote for optimal cache use. Using squid (200MB process in my case) can be much faster if squid stays on the same CPU for a while, instead of hopping from one CPU to another (dual PII350 machine).
François Cami
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