[Xen-devel] Credit Scheduler

[gaurav somani <onlineengineer@xxxxxxxxx>]

Hi all,


I am just trying to understand the credit scheduler in xen.
please correct me in below sequence .
There are four VMs named V1 to V4. each having 256 credits. t is the CPU time.



                        V1                    V2                V3                       V4

t=0                      256                 256                 256                    256
t=10                    156                 256                 256                    256




t=20                     56                  256                 256                    256
t=30                    -44                  256                 256                    256

t=40                    -44                 156                256                    256



t=50                    -44                 56                256                    256
t=60                     -44                -44                 256                    256

t=70                    -44                  -44               156                    256
t=80                    -44                  -44               56                    256

t=90                    -44                  -44               -44                    256

t=100                    -44                  -44               -44                    156

t=110                    -44                  -44               -44                    56


t=120                    -44                  -44               -44                    -44

Credits will be re assigned when some of all credits becomes negative.
what I understand from the BOOST state is. According to I/O event mapping in event channel, if the domain corresponding to that I/O event is in UNDER state than it can be upgraded to BOOST state which is highest priority state in xen.

So currently running domain will be preempted and BOOSTED domain will receive the CPU.

I am having some questions
(1) How many credits are deducted from a VM in a BOOSTed state?
(2) If a VM has the work only for 10 ms, then what happens? Will it go to idle state? after 10 secs or it will consume whole 30 secs slice?

Please provide me the direction.

Regards 
 
Gaurav somani
Dhirubhai Ambani Institute of ICT,
Gandhinagar
Gujarat, INDIA
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