[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] xen 4.5.0 rtds scheduler perform poorly with 2vms
2015-11-27 14:50 GMT-05:00 Yu-An(Victor) Chen <chen116@xxxxxxx>: > 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. What is the characteristics of tasks you generated? When a taskset miss ddl., which task inside miss deadline? Meng > > 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 <xumengpanda@xxxxxxxxx> wrote: >> >> 2015-11-27 12:23 GMT-05:00 Dario Faggioli <dario.faggioli@xxxxxxxxxx>: >> > 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 > > -- ----------- Meng Xu PhD Student in Computer and Information Science University of Pennsylvania http://www.cis.upenn.edu/~mengxu/ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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