An HTML attachment was scrubbed... URL: http://sos.ece.cmu.edu/pipermail/simflex/attachments/20060202/ef629b0b/attachment.html From jsmolens+ at ece.cmu.edu Thu Feb 2 12:07:30 2006 From: jsmolens+ at ece.cmu.edu (Jared C. Smolens) List-Post: [email protected] Date: Thu Feb 2 12:07:35 2006 Subject: [Simflex] About Piranha Cache Message-ID: <[email protected]>
Hi Lu, Yes, the simulation model maintains a PiranhaDirEntry for every valid line in the CMP (in one or more L1s, L2, or both). To fully determine where the line is, you need to consider its state, it's owner, and the l2Lookup structure: theOwner points to a cache which can supply a coherent value for the line. For the Shared and Owner states, it's safe to read the L2 value if l2Lookup shows a hit, since all copies of the line must be identical in these states. If l2Lookup shows a miss, follow theOwner to the correct L1. For the Modified state, always follow theOwner (set to the core index or -1 if the L2 owns the line). Jared Excerpts From "lu peng" <[email protected]>: Re: [Simflex] About Piranha Cache: "lu peng" <[email protected]> ><P>Hi, Jared,</P> ><P>How are you? I have some further questions about the Piranha Directory >. </P> ><P>1. Because the Piranha Cache doesn't have inclusion property, it also has&n >bsp;to snoop L1 cache for coherency. Does it create a PiranhaDirEntry for each > L1 cache block for snooping? If not, how does it snoop? </P> ><P>2. You mentioned that "Compaq's Piranha uses duplicate L1 tags at the L2 to > track the same information" above. Related to the source code, does this mean > create a PiranhaDirEntry for each L1 cache block?</P> ><P>3. If so, how do I distinguish an Entry which points to an L1 line or an L2 > line? Do you use the 'theOwner' field in the struct of PiranhaDirEntry? If no >t, what does 'theOwner' mean?</P> ><P>Thanks a lot,</P> ><P>Lu</P></FONT></DIV></div></html> Jared Smolens ----------- Electrical and Computer Engineering www.rabidpenguin.org ------------- Carnegie Mellon University jsmolens AT ece.cmu.edu ------ HH A-313 ------ Pittsburgh, PA
