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Date: Tue, 17 Oct 2006 12:18:23 -0700 From: Paul Jackson <pj@....com> To: "Siddha, Suresh B" <suresh.b.siddha@...el.com> Cc: dino@...ibm.com, suresh.b.siddha@...el.com, menage@...gle.com, Simon.Derr@...l.net, linux-kernel@...r.kernel.org, mbligh@...gle.com, rohitseth@...gle.com, dipankar@...ibm.com Subject: Re: [RFC] Cpuset: explicit dynamic sched domain control flags > What happens when the job in the cpuset with no sched domain > becomes active? In this case, scheduler can't make use of all cpus > that this cpuset is allowed to use. What happens then is that the job manager marks the cpuset of this newly activated job as being a sched_domain. And if the job manager doesn't do that, and sets up a situation in which the scheduler domains don't line up with the active jobs, then they can't get scheduler load balancing across all the CPUs in those jobs cpusets. That's exactly what they asked for -- that's exactly what they got. (Actually, is that right? I thought load balancing would still occur at higher levels in the sched domain/group hierarchy, just not as often.) It is not the kernels job to make it impossible for user code to do stupid things. It's the kernels job to offer up various mechanisms, and let user space code decide what to do when. And, anyhow, how does this differ from overloading the cpu_exclusive flag to define sched domains. One can setup the same thing there, where a job can't balance across all its CPUs: /dev/cpuset/cs1 cpu_exclusive = 1; cpus = 0-7 /dev/cpuset/cs1/suba cpu_exclusive = 1; cpus = 0-3 /dev/cpuset/cs1/subb cpu_exclusive = 1; cpus = 4-7 (sched_domain_enabled = 0 in all cpusets) If you put a task in cpuset "cs1" (not in one of the sub cpusets) then it can't load balance between CPUs 0-3 and CPUs 4-7 (or can't load balance as often - depending on how this works.) -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@....com> 1.925.600.0401 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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