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Dario Faggioli
d671da3be3
In cases where one is absolutely sure that there will be less vCPUs than pCPUs, having to pay the cost, mostly in terms of overhead, of an advanced scheduler may be not desirable. The simple scheduler implemented here could be a solution. Here how it works: - each vCPU is statically assigned to a pCPU; - if there are pCPUs without any vCPU assigned, they stay idle (as in, the run their idle vCPU); - if there are vCPUs which are not assigned to any pCPU (e.g., because there are more vCPUs than pCPUs) they *don't* run, until they get assigned; - if a vCPU assigned to a pCPU goes away, one of the waiting to be assigned vCPU, if any, gets assigned to the pCPU and can run there. This scheduler, therefore, if used in configurations where every vCPUs can be assigned to a pCPU, guarantees low overhead, low latency, and consistent performance. If used as default scheduler, at Xen boot, it is recommended to limit the number of Dom0 vCPUs (e.g., with 'dom0_max_vcpus=x'). Otherwise, all the pCPUs will have one Dom0's vCPU assigned, and there won't be room for running efficiently (if at all) any guest. Target use cases are embedded and HPC, but it may well be interesting also in circumnstances. Kconfig and documentation are update accordingly. While there, also document the availability of sched=rtds as boot parameter, which apparently had been forgotten. Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com> Reviewed-by: George Dunlap <george.dunlap@citrix.com>
xen-bugtool =========== The xen-bugtool command line application will collate the Xen dmesg output, details of the hardware configuration of your machine, information about the build of Xen that you are using, plus, if you allow it, various logs. The information collated can either be posted to a Xen Bugzilla bug (this bug must already exist in the system, and you must be a registered user there), or it can be saved as a .tar.bz2 for sending or archiving. The collated logs may contain private information, and if you are at all worried about that, you should not use this tool, or you should explicitly exclude those logs from the archive. xen-bugtool is wholly interactive, so simply run it, and answer the questions.