Hi Meng, Thank you so much for being this patience.
So a task set is composed of a collection of real-time tasks, and each real-time task is a sequence of jobs that are released periodically... All jobs are periodic, where each job Ti is defined by a period (and deadline) pi and a worse-case execution time ei, with pi ≥ ei ≥ 0 and pi, ei ∈ integers. Each job is comprised of a number of iterations of floating point operations during each job. This is based on the base task.c provided with the LITMUSRT userspace library. So in a tasks set, there are many tasks, and in each tasks, there are a sequence of jobs, if any job misses deadline, then the whole taskset is qualified as failed to be schedulable. Thank you Victor On Fri, Nov 27, 2015 at 4:17 PM, Meng Xu <xumengpa...@gmail.com> wrote: > 2015-11-27 14:50 GMT-05:00 Yu-An(Victor) Chen <chen...@usc.edu>: > > 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 <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 > > > > > > > > -- > > > ----------- > Meng Xu > PhD Student in Computer and Information Science > University of Pennsylvania > http://www.cis.upenn.edu/~mengxu/ >
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