Hi Dario & Meng, Thanks for your analysis!
VM1 and VM2 both are given 8 vCPUs and sharing physical CPU 0-7. So in theory,"VM1 can get the services of 400%" And yes, Dario, your explanation about the task utilization is correct. So the resource configuration as I mentioned before is: for xen-credit : 2vms (both vm are given 8 vCPUs) sharing 8 cores (cpu 0-7) using credit scheduler(both with weight of 800 and capacity of 400) for xen-rtds: 2 vms (both vm are given 8 vCPUs) sharing 8 cores (cpu0-7) using RTDS (both with period of 10000 and budget of 5000) In both setup, dom0 is using 1 core from cpu 8-15 In both setup: I loaded VM2 with constant running task with total utilization of 4 cores. and in VM1 I run iterations of tasks of total utilization rate of 1 cores, 2 cores, 3 cores, 4 cores, and then record their schedulbility. Attached is the result plot. I have tried with the newest litmust-rt, and rtxen is still performing poorly. Thank you both very much again, if there is any unclear part, please lemme know, thx! Victor On Fri, Nov 27, 2015 at 9:41 AM, Meng Xu <xumengpa...@gmail.com> wrote: > 2015-11-27 12:23 GMT-05:00 Dario Faggioli <dario.faggi...@citrix.com>: > > On Fri, 2015-11-27 at 08:36 -0800, Yu-An(Victor) Chen wrote: > >> Hi Dario, > >> > > Hi, > > > >> Thanks for the reply! > >> > > You're welcome. :-) > > > > I'm adding Meng to Cc... > > > > Thanks! :-) > > >> My goal for the experiment is to show that xen rtds scheduler is > >> better than credit scheduler when it comes to real time tasks. > >> so my set up is: > >> > >> for xen-credit : 2vms sharing 8 cores (cpu 0-7) using credit > >> scheduler(both with weight of 800 and capacity of 400) > > So you set up 400% cpu cap for each VM. In other words, each VM will > have computation capacity almost equal to 4 cores. Because VCPUs are > also scheduled, the four-core capacity is not equal to 4 physical core > in bare metal, because the resource supplied to tasks from VCPUs also > depend on the scheduling pattern (which affect the resource supply > pattern) of the VCPUs. > > >> for xen-rtds: 2 vms sharing 8 cores (cpu0-7) using RTDS (both with > >> period of 10000 and budget of 5000) > > How many VCPUs for each VM? If each VM has 4 VCPU, each VM has only > 200% CPU capacity, which is only half compared to the configuration > you made for credit scheduler. > > >> in both setup, dom0 is using 1 core from cpu 8-15 > > Do you have some quick evaluation report (similar to the evaluation > section in academic papers) that describe how you did the experiments, > so that we can have a better guess on where goes wrong. > > Right now, I'm guessing that: the resource configured for each VM > under credit and rtds schedulers are not the same, and it is possible > that some parameters are not configured correctly. > > Another thing is that: > credit scheduler is work conserving, while RTDS is not. > So under the under-loaded situation, you will see credit scheduler may > work better because it try to use as much resource as it could. You > can make the comparision more failrly by setting the cap for credit > scheduler as you did, and running some background VM or tasks to > consume the idle resource. > > Meng >
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