Hi Prathap,

100 was chosen to be “sufficiently infinite”, and only break if something is 
wrong.

The caches have a limited number of MSHRs, the cores have limited LSQ depth 
etc. We could easily add an outstanding transaction limit to the crossbar 
class. In the end it is a detail/speed trade-off. If it does not matter, do not 
model it…

Andreas

From: gem5-users 
<[email protected]<mailto:[email protected]>> on behalf of 
Prathap Kolakkampadath <[email protected]<mailto:[email protected]>>
Reply-To: gem5 users mailing list 
<[email protected]<mailto:[email protected]>>
Date: Monday, 27 July 2015 15:15
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: Re: [gem5-users] How queued port is modelled in real platforms?

Hello Andreas,

Currently, the reasonable limit of this queue is set to 100. Is there a 
specific reason to choose this as the maximum packet queue size.
Do any bus interface protocol specifies this limit in real platforms?

Thanks,
Prathap

On Mon, Jul 27, 2015 at 4:54 AM, Andreas Hansson 
<[email protected]<mailto:[email protected]>> wrote:
Hi Prathap,

The queued port is indeed infinite, and is a convenience construct. It should 
only be used in places where there is already an inherent limit to the number 
of outstanding requests. There is an assert in the queued port to ensure things 
do not grow uncontrollably.

Andreas

From: gem5-users 
<[email protected]<mailto:[email protected]>> on behalf of 
Prathap Kolakkampadath <[email protected]<mailto:[email protected]>>
Reply-To: gem5 users mailing list 
<[email protected]<mailto:[email protected]>>
Date: Sunday, 26 July 2015 18:34
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: [gem5-users] How queued port is modelled in real platforms?

Hell Users,

Gem5 implements a queued port to interface memory objects. In my understanding 
this queued port is of infinite size. Is this specific to Gem5 implementation? 
How packets are handled in real hardware if the request rate of a layer is 
faster than the service rate of underlying layer?
It would be great if someone could help me in understanding this.

Thanks,
Prathap



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