gem5 - gem5

Age	Commit message (Collapse)	Author
2015-07-03	mem: Delay responses in the crossbar before forwarding	Andreas Hansson
	This patch changes how the crossbar classes deal with responses. Instead of forwarding responses directly and burdening the neighbouring modules in paying for the latency (through the pkt->headerDelay), we now queue them before sending them. The coherency protocol is not affected as requests and any snoop requests/responses are still passed on in zero time. Thus, the responses end up paying for any header delay accumulated when passing through the crossbar. Any latency incurred on the request path will be paid for on the response side, if no other module has dealt with it. As a result of this patch, responses are returned at a later point. This affects the number of outstanding transactions, and quite a few regressions see an impact in blocking due to no MSHRs, increased cache-miss latencies, etc. Going forward we should be able to use the same concept also for snoop responses, and any request that is not an express snoop.
2014-04-25	mem: Add access statistics for the snoop filter	Stephan Diestelhorst
	Adds a simple access counter for requests and snoops for the snoop filter and also classifies hits based on whether a single other holder existed or whether multiple shares held the line.
2014-09-20	mem: Simple Snoop Filter	Stephan Diestelhorst
	This is a first cut at a simple snoop filter that tracks presence of lines in the caches "above" it. The snoop filter can be applied at any given cache hierarchy and will then handle the caches above it appropriately; there is no need to use this only in the last-level bus. This design currently has some limitations: missing stats, no notion of clean evictions (these will not update the underlying snoop filter, because they are not sent from the evicting cache down), no notion of capacity for the snoop filter and thus no need for invalidations caused by capacity pressure in the snoop filter. These are planned to be added on top with future change sets.