[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2] xen: sched_credit: filter node-affinity mask against online cpus
On 17/09/13 16:16, Dario Faggioli wrote: in _csched_cpu_pick(), as not doing so may result in the domain's node-affinity mask (as retrieved by csched_balance_cpumask() ) and online mask (as retrieved by cpupool_scheduler_cpumask() ) having an empty intersection. Therefore, when attempting a node-affinity load balancing step and running this: ... /* Pick an online CPU from the proper affinity mask */ csched_balance_cpumask(vc, balance_step, &cpus); cpumask_and(&cpus, &cpus, online); ... we end up with an empty cpumask (in cpus). At this point, in the following code: .... /* If present, prefer vc's current processor */ cpu = cpumask_test_cpu(vc->processor, &cpus) ? vc->processor : cpumask_cycle(vc->processor, &cpus); .... an ASSERT (from inside cpumask_cycle() ) triggers like this: (XEN) Xen call trace: (XEN) [<ffff82d08011b124>] _csched_cpu_pick+0x1d2/0x652 (XEN) [<ffff82d08011b5b2>] csched_cpu_pick+0xe/0x10 (XEN) [<ffff82d0801232de>] vcpu_migrate+0x167/0x31e (XEN) [<ffff82d0801238cc>] cpu_disable_scheduler+0x1c8/0x287 (XEN) [<ffff82d080101b3f>] cpupool_unassign_cpu_helper+0x20/0xb4 (XEN) [<ffff82d08010544f>] continue_hypercall_tasklet_handler+0x4a/0xb1 (XEN) [<ffff82d080127793>] do_tasklet_work+0x78/0xab (XEN) [<ffff82d080127a70>] do_tasklet+0x5f/0x8b (XEN) [<ffff82d080158985>] idle_loop+0x57/0x5e (XEN) (XEN) (XEN) **************************************** (XEN) Panic on CPU 1: (XEN) Assertion 'cpu < nr_cpu_ids' failed at /home/dario/Sources/xen/xen/xen.git/xen/include/xe:16481 It is for example sufficient to have a domain with node-affinity to NUMA node 1 running, and issueing a `xl cpupool-numa-split' would make the above happen. That is because, by default, all the existing domains remain assigned to the first cpupool, and it now (after the cpupool-numa-split) only includes NUMA node 0. This change prevents that by generalizing the function used for figuring out whether a node-affinity load balancing step is legit or not. This way we can, in _csched_cpu_pick(), figure out early enough that the mask would end up empty, skip the step all together and avoid the splat. Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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