Messages in this thread | | | Date | Mon, 21 Aug 2006 22:14:37 -0700 | From | Paul Jackson <> | Subject | Re: cpusets not cpu hotplug aware |
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Nathan wrote: > I think it would be more sensible for the default (i.e. user hasn't > explicitly configured any cpusets) behavior on a CONFIG_CPUSETS=y > kernel to match the behavior with a CONFIG_CPUSETS=n kernel.
Basically, in this situation, that would mean that the code that masks a requested sched_setaffinity cpumask with the tasks cpuset_cpus_allowed():
cpus_allowed = cpuset_cpus_allowed(p); cpus_and(new_mask, new_mask, cpus_allowed);
would not be executed in the case of a kernel configured for cpusets, when running on a system that wasn't using cpusets.
That's quite doable, and for systems not actually using cpusets, makes good sense.
But it makes a bit of discontinuity in the system behaviour when someone starts using cpusets. If someone makes a cpuset, then suddenly tasks in the top cpuset start seeing failed sched_setaffinity calls for any CPU that was brought online after system boot.
If there is some decent way I can get the cpus_allowed of the top cpuset to track the cpu_online_map, then we avoid this discontinuity in system behaviour.
-- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@sgi.com> 1.925.600.0401 - 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/
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