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path: root/src/mem/xbar.cc
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2015-07-07sim: Refactor and simplify the drain APIAndreas Sandberg
The drain() call currently passes around a DrainManager pointer, which is now completely pointless since there is only ever one global DrainManager in the system. It also contains vestiges from the time when SimObjects had to keep track of their child objects that needed draining. This changeset moves all of the DrainState handling to the Drainable base class and changes the drain() and drainResume() calls to reflect this. Particularly, the drain() call has been updated to take no parameters (the DrainManager argument isn't needed) and return a DrainState instead of an unsigned integer (there is no point returning anything other than 0 or 1 any more). Drainable objects should return either DrainState::Draining (equivalent to returning 1 in the old system) if they need more time to drain or DrainState::Drained (equivalent to returning 0 in the old system) if they are already in a consistent state. Returning DrainState::Running is considered an error. Drain done signalling is now done through the signalDrainDone() method in the Drainable class instead of using the DrainManager directly. The new call checks if the state of the object is DrainState::Draining before notifying the drain manager. This means that it is safe to call signalDrainDone() without first checking if the simulator has requested draining. The intention here is to reduce the code needed to implement draining in simple objects.
2015-03-02mem: Add crossbar latenciesMarco Balboni
This patch introduces latencies in crossbar that were neglected before. In particular, it adds three parameters in crossbar model: front_end_latency, forward_latency, and response_latency. Along with these parameters, three corresponding members are added: frontEndLatency, forwardLatency, and responseLatency. The coherent crossbar has an additional snoop_response_latency. The latency of the request path through the xbar is set as --> frontEndLatency + forwardLatency In case the snoop filter is enabled, the request path latency is charged also by look-up latency of the snoop filter. --> frontEndLatency + SF(lookupLatency) + forwardLatency. The latency of the response path through the xbar is set instead as --> responseLatency. In case of snoop response, if the response is treated as a normal response the latency associated is again --> responseLatency; If instead it is forwarded as snoop response we add an additional variable + snoopResponseLatency and the latency associated is --> snoopResponseLatency; Furthermore, this patch lets the crossbar progress on the next clock edge after an unused retry, changing the time the crossbar considers itself busy after sending a retry that was not acted upon.
2015-03-02mem: Split port retry for all different packet classesAndreas Hansson
This patch fixes a long-standing isue with the port flow control. Before this patch the retry mechanism was shared between all different packet classes. As a result, a snoop response could get stuck behind a request waiting for a retry, even if the send/recv functions were split. This caused message-dependent deadlocks in stress-test scenarios. The patch splits the retry into one per packet (message) class. Thus, sendTimingReq has a corresponding recvReqRetry, sendTimingResp has recvRespRetry etc. Most of the changes to the code involve simply clarifying what type of request a specific object was accepting. The biggest change in functionality is in the cache downstream packet queue, facing the memory. This queue was shared by requests and snoop responses, and it is now split into two queues, each with their own flow control, but the same physical MasterPort. These changes fixes the previously seen deadlocks.
2015-02-11mem: Clarification of packet crossbar timingsMarco Balboni
This patch clarifies the packet timings annotated when going through a crossbar. The old 'firstWordDelay' is replaced by 'headerDelay' that represents the delay associated to the delivery of the header of the packet. The old 'lastWordDelay' is replaced by 'payloadDelay' that represents the delay needed to processing the payload of the packet. For now the uses and values remain identical. However, going forward the payloadDelay will be additive, and not include the headerDelay. Follow-on patches will make the headerDelay capture the pipeline latency incurred in the crossbar, whereas the payloadDelay will capture the additional serialisation delay.
2014-09-27mem: Output precise range when XBar has conflictsCurtis Dunham
2014-09-20mem: Rename Bus to XBar to better reflect its behaviourAndreas Hansson
This patch changes the name of the Bus classes to XBar to better reflect the actual timing behaviour. The actual instances in the config scripts are not renamed, and remain as e.g. iobus or membus. As part of this renaming, the code has also been clean up slightly, making use of range-based for loops and tidying up some comments. The only changes outside the bus/crossbar code is due to the delay variables in the packet. --HG-- rename : src/mem/Bus.py => src/mem/XBar.py rename : src/mem/coherent_bus.cc => src/mem/coherent_xbar.cc rename : src/mem/coherent_bus.hh => src/mem/coherent_xbar.hh rename : src/mem/noncoherent_bus.cc => src/mem/noncoherent_xbar.cc rename : src/mem/noncoherent_bus.hh => src/mem/noncoherent_xbar.hh rename : src/mem/bus.cc => src/mem/xbar.cc rename : src/mem/bus.hh => src/mem/xbar.hh