Re: [GridSim-users] Question regarding simulation time

[<ag...@ds...>]

Hi Chainan,

I think I can give some hints to fix your problem.

First, you say that "- Gridlet#0 size 1000 submitted at 11.00 starts at 
11.00 ". This means, to my understanding, that the gridlet is being 
submitted at time 11.00 and its execution starts at 11.00. This means 
that the second 11.00 includes the network transmission time + the time 
to wait for a idle PE at the resource. Since this is the first gridlet, 
all PEs are idle so it starts being executed straight-away.
If u pay attention, the start time is the same as the submission time 
for the first 3 gridlets in your sims, because your resource has 3 PEs.
Delays begin when all the PEs are busy, so they are created because of 
congestion at the resource.

In order to test the network performance, you can create a bigger 
resource (with more PEs) so that time differences between gridlets will 
be caused by the network transmission, not by contention at the 
resource. If there are no differences, try making the gridlets IO files 
bigger.

Hope this is useful.

All the best,

Agustin

Chainan Satayapiwat escribio':
> Hi,
>
> I was studying the sample code which provided in
> http://www.gridbus.org/gridsim/example/index.html Specifically, my
> problem was coming from the example 7 (Test.java & TestCase1.java) when
> running the simulation. The allocation policy was space sharing.
>
> There are 2 users (User_0 and User_1) I saw all the Gridlet from User_0
> start queuing for processing earlier than User_1 but the lenght of
> Gridlet (which seems to use as Gridlet size, in_file size, and out_file
> size) are all the same. Given the User_1 has 5 times higher bandwidth,
> then, I would assume that the User_1 start time should be earlier than
> User_0. However, here are the result of simulation
>
> Here are the detail.
> All Gridlet schedules onto 1 Machine with 3 PEs.
> User_0 (Bandwidth 1000) has
> 	- Gridlet#0 size 1000 submitted at 11.00 starts at 11.00
> 	- Gridlet#1 size 2000 submitted at 35.00 starts at 35.00
> 	- Gridlet#2 size 3000 submitted at 75.00 starts at 120.00
> 	- Gridlet#3 size 4000 submitted at 131.00 starts at 313.00
>
> User_1 (Bandwidth 5000) has
> 	- Gridlet#0 size 1000 submitted at 19.00 starts at 19.00
> 	- Gridlet#1 size 2000 submitted at 51.00 starts at 112.00
> 	- Gridlet#2 size 3000 submitted at 99.00 starts at 236.00
> 	- Gridlet#3 size 4000 submitted at 163.00 starts at 421.00
>
> As shown above, I can't understand how it works here. User with higher
> bandwidth should be able to finish uploading the file to the processing
> machine first and, thus, the job should be ready to submit earlier.
> Therefore, I tried to make sure if this is about bandwidth things by
> hardcode in the TestCase1.java in createGridlet method by fixing the
> size of input file. (i.e. third parameter of Gridlet constructor) As
> expected, all Gridlet starts at 3rd second of simulation time. (This is
> considered immediate as the code wait 3 units of time in the beginning)
> So, I'm quite sure that the delay is coming from the simulation of file
> transfer that required before the program execution. So, why the higher
> bandwidth is slower? Perhaps, I misunderstood at some points and confuse
> myself. Could anyone kindly help me out on this?
>
> Thank you.
>
> Best Regards,
> Chainan Satayapiwat
> Research Student, Tohoku University
>
>
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-- 
========================================================
Agustin Caminero
PhD Student
Computing Systems Department
The University of Castilla La Mancha, Albacete. Spain.
Phone: +34 967 599 200 Ext. 2693. Fax: +34 967 599 343
http://www.i3a.uclm.es/
========================================================