[Disksim-users] System Level Simulation

[vahldiek at mpi-sws.org]

Hi,

I have seen the behavior before and studied the execution of the syssim.
you will see differences at the level of the disksim_diskctlr. These
differences come from an issue within the current syssim implementation in
which the following happens:
1) a request is inserted into disksim
2) the request is handled
3) the method to report completion is called

Until now everything seems fine, if the next request would immediately
start after the request completion method is called. Unfortunately this is
not the case, the syssim stays within the loop processing disksim events.
/* Process events until this I/O is completed */
while(next_event >= 0) {
 now = next_event;
 next_event = -1;
 disksim_interface_internal_event(disksim, now, 0);
}

Why is this the case? The request is fully processed so there shouldn't be
any events within the system, right?
Disksim adds an event automatically after every request to continue
reading after the request is over. This is done at the disksim_diskctlr
level and continues until the segment storing the request is full.

For me this meant a difference in completion time and next starting time
of around 0.5ms.

To address the issue I think I added && completion == 0 to the while loop.
This should stop the loop when the request is completed. All other events
will not be taken into account then. You may run into trouble, if you
insert multiple requests starting nearly at the same time.

I hope this helps...

Regards,
Anjo

> Hi,
>
> I am doing a simulation using disksim as a blackbox (using Disksim in
> system level simulation as suggested in page 44 of the manual). Here is
> the
> situation:
>
> I am using the same trace and .parv files to do an interface simulation
> and
> an internal simulation. Both of them are giving different results. When I
> observed the output event files I found that the event sequence is a lot
> different in both the scenarios and I have no idea why it is happening so.
> My doubt is can this happen, given that I am using the same input?
>
> Any help will be greatly appreciated.
>
> --
> Regards,
> Purushotham
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