Re: [Gems-users] Protocol with Directory Cache (again)

["Liqun Cheng" <liqun.cheng@xxxxxxxxx>]

Mike,

thanks, I will do in this way. Just make sure I need to add this if.. else in every action, right?

Legion

On 2/20/07, Mike Marty <mikem@xxxxxxxxxxx> wrote:

I've added a directory cache to one of my own protocols.  I added no
states.  Here is an example action.  Notice all it does is check to see if
dirCache contains the tag.  If so, it uses DIRECTORY_CACHE_LATENCY instead
of DIRECTORY_LATENCY


  action(f_forwardRequest, "f", desc="Forward request to owner") {
    peek(requestQueue_in, RequestMsg) {
      if (dirCache.isTagPresent(address) == false) {
        enqueue(forwardNetwork_out, RequestMsg,
latency="DIRECTORY_LATENCY") {
          out_msg.Address := address;
          out_msg.Type := in_msg.Type;
          out_msg.Requestor := in_msg.Requestor;
          out_msg.Destination.addNetDest(directory[in_msg.Address].Owner);
          out_msg.AckCount := directory[address].Sharers.count();
          if
(directory[address].Sharers.isElement(map_L1CacheMachId_to_PrivateL2Cache(in_msg.Requestor)))
{
            out_msg.AckCount := out_msg.AckCount - 1;
          }
          APPEND_TRANSITION_COMMENT(in_msg.Requestor);
          APPEND_TRANSITION_COMMENT(" ");
          APPEND_TRANSITION_COMMENT(directory[in_msg.Address].Owner);
          out_msg.MessageSize := MessageSizeType:Forwarded_Control;
        }
      } else {
        enqueue(forwardNetwork_out, RequestMsg,
latency="DIRECTORY_CACHE_LATENCY") {
          out_msg.Address := address;
          out_msg.Type := in_msg.Type;
          out_msg.Requestor := in_msg.Requestor;
          out_msg.Destination.addNetDest(directory[in_msg.Address].Owner);
          out_msg.AckCount := directory[address].Sharers.count();
          if
(directory[address].Sharers.isElement(map_L1CacheMachId_to_PrivateL2Cache(in_msg.Requestor)))
{
            out_msg.AckCount := out_msg.AckCount - 1;
          }
          APPEND_TRANSITION_COMMENT(in_msg.Requestor);
          APPEND_TRANSITION_COMMENT(" ");
          APPEND_TRANSITION_COMMENT(directory[in_msg.Address].Owner);
          out_msg.MessageSize := MessageSizeType:Forwarded_Control;
        }
      }
    }
  }



> Hi,
>
> I finally make the RAC work, at least the tester and splash2 didn't compain.
> thanks for the helps.
> Now I plan to add a directory cache. I do find one thread on this topic in
> the archive, and Mike recommended:
> "You can change the getState() function in the Directory controller to return
> a different state if the directory entry
> is cached. Actions triggered by events to these cached states will use a
> lower latency".
>
> However, I have concerns to the above solution. First, we need to duplicate
> all Actions/Transitions and make changes
> everywhere. Second, maintaining a seperate set of states for directory cache
> is quite nontrivial, may even raise problems
> at directory cache replacement. Therefore, I prefer to make changes in a
> centralized place.
>
> Here are my random thoughts. In getState, if we make directory cache hit as
> the base case, and add some
> latency (directory latency - directory cache hit latency) at misses, this
> should be a close approximation. However, since
> getState is not an event, I don't find a easy way to recycle (retry after xx
> cycles) it.  As a result,  I am thinking of adding
> latency when poping the message from in-port. Basically, we add a new
> function in MessageBuffer class say
> cust-recycle(num_cycles). When peeking in-ports, we first check the
> directory cache. If tag matches, we pop the messages
> as usual, else, we cust-recycle this message for (directory latency -
> directory caches hit latency) cycles. Will this work?
>
> you guys are much more experienced on gems, any feedback/advice is much
> appreciated.
>
> thanks
> Legion
>
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