Re: [Gems-users] How to config memory system

["张轶" <zhangyi@xxxxxxxxxxxxxx>]

Hi Dan,

 

I have performed such a experiment: print out all the banks a memory controller accessed, in MOSI_SMP_bcast_m protocol, with 2 processors.  

 

The result shows that all the banks can be accessed by both memory controllers.

 

In the real DRAM system, the banks accessed by one channel can not be accessed by another channel and accesses between different channels won't be stalled. Since in GEMS, memory controller = channel, then if, at the same time, each memory controller/channel can access all the banks, what is the mechanism of the memory controller in GEMS? Is it right to say in GEMS, there happens that multiple accesses from different channels contend for one bank?

 

Best Regards,

 

Zhang Yi

------------------ Original ------------------

From:  "Dan Gibson"<degibson@xxxxxxxx>;

Date:  Wed, Apr 7, 2010 10:03 PM

To:  "Gems Users"<gems-users@xxxxxxxxxxx>;

Subject:  Re: [Gems-users] How to config memory system

 

I believe the bits that determine which controller to use are hard-coded into Ruby.Look at the function map_Address_to_DirectoryNode in RubySlicc_ComponentMapping.h.

Regards,
Dan

2010/4/7 张轶 <zhangyi@xxxxxxxxxxxxxx>

Hi Dan,

 

I have read rubyconfig.defaults carefully and do some experiments. It seems that the address mapping that determines which bits to denote the channel dosen't appear in the rubyconfig.defaults.

 

You mean the address mappings for channel bits should be configured in topology files, right? Would you tell me which files I should refer to?

 

Thanks,

 

Zhang Yi

------------------ Original ------------------

From:  "Dan Gibson"<degibson@xxxxxxxx>;

Date:  Tue, Apr 6, 2010 10:04 PM

To:  "Gems Users"<gems-users@xxxxxxxxxxx>;

Subject:  Re: [Gems-users] How to config memory system

 

1. In rubyconfig.defaults, there are 17 configuration variables affecting the MemoryController. Read the comments.
2. The number of memory controllers will depend on your topology.

Regards,
Dan

2010/4/6 张轶 <zhangyi@xxxxxxxxxxxxxxx>

Hi Dan,

 

Thanks for your help. But unfortunately, I am still not clear how to configure the memory controller.

1)In the rubyconfig.defaults, there is no configurations for the memory controller/channel. So how to assign which address bits to denote channels?

 

2)My system is configured with MOSI_SMP_bcast_m protocol, 2 processors... The other settings are followed by rubyconfig.defaults. BANKS_PER_RANK: 8, RANKS_PER_DIMM: 2, DIMMS_PER_CHANNEL: 2 ....

In the memorycontrol instantiation, I have added an random function, and through the data printed out, I suppose there should be two memory controllers/channels, thus there would be totally 64 banks, doubles of 32.

But through typing command dump-stats, I could only read 32 banks, namely half statistics.

So, why?

 

Any advice will be appreciated!

 

Zhang Yi

 

 

------------------ Original ------------------

From:  "Dan Gibson"<degibson@xxxxxxxx>;

Date:  Sat, Apr 3, 2010 10:43 PM

To:  "Gems Users"<gems-users@xxxxxxxxxxx>;

Subject:  Re: [Gems-users] How to config memory system

 

1. The number of memory controllers is a function of the network topology. They appear in the topology as "Directory Memory" objects. This is true regardless of whether you happen to be using a 'CMP' or 'SMP' protocol.
2. Memory controllers are shared by all processors.
3. In GEMS, Memory Controller = Memory Channel.

Bonus extra response: Only protocols that end in _m actually use a realistic memory controller. All other protocols just assume memory has a fixed latency.

Regards,
Dan

2010/4/3 张轶 <zhangyi@xxxxxxxxxxxxxx>

Hi, all

Currently, I am using GEMS 2.1 to perform simulation andhavesome confusions on memory configs:

1. I am wondering, inGEMShow to set the numbers ofmemory controllerfor CMP and SMP system? Isit the same in both CMP and SMP?

2. Will memory controller be shared by all processors?

3.Is memory controller the same thingto memory channels?

Many thanks for your help!

Zhang Yi

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