summaryrefslogtreecommitdiff
path: root/src/mem/cache/base.hh
AgeCommit message (Collapse)Author
2015-05-27mem: Add unused prefetch counter in cachesRekai Gonzalez Alberquilla
Added stat to the cache to account for HardPF'ed blocks that are evicted before being referenced (over-prefetching).
2016-03-17mem: Create a separate class for the cache write bufferAndreas Hansson
This patch breaks out the cache write buffer into a separate class, without affecting any stats. The goal of the patch is to avoid encumbering the much-simpler write queue with the complex MSHR handling. In a follow on patch this simplification allows us to implement write combining. The WriteQueue gets its own class, but shares a common ancestor, the generic Queue, with the MSHRQueue.
2016-02-10mem: Deduce if cache should forward snoopsAndreas Hansson
This patch changes how the cache determines if snoops should be forwarded from the memory side to the CPU side. Instead of having a parameter, the cache now looks at the port connected on the CPU side, and if it is a snooping port, then snoops are forwarded. Less error prone, and less parameters to worry about. The patch also tidies up the CPU classes to ensure that their I-side port is not snooping by removing overrides to the snoop request handler, such that snoop requests will panic via the default MasterPort implement
2015-12-31mem: Make cache terminology easier to understandAndreas Hansson
This patch changes the name of a bunch of packet flags and MSHR member functions and variables to make the coherency protocol easier to understand. In addition the patch adds and updates lots of descriptions, explicitly spelling out assumptions. The following name changes are made: * the packet memInhibit flag is renamed to cacheResponding * the packet sharedAsserted flag is renamed to hasSharers * the packet NeedsExclusive attribute is renamed to NeedsWritable * the packet isSupplyExclusive is renamed responderHadWritable * the MSHR pendingDirty is renamed to pendingModified The cache states, Modified, Owned, Exclusive, Shared are also called out in the cache and MSHR code to make it easier to understand.
2015-11-06mem: Add an option to perform clean writebacks from cachesAndreas Hansson
This patch adds the necessary commands and cache functionality to allow clean writebacks. This functionality is crucial, especially when having exclusive (victim) caches. For example, if read-only L1 instruction caches are not sending clean writebacks, there will never be any spills from the L1 to the L2. At the moment the cache model defaults to not sending clean writebacks, and this should possibly be re-evaluated. The implementation of clean writebacks relies on a new packet command WritebackClean, which acts much like a Writeback (renamed WritebackDirty), and also much like a CleanEvict. On eviction of a clean block the cache either sends a clean evict, or a clean writeback, and if any copies are still cached upstream the clean evict/writeback is dropped. Similarly, if a clean evict/writeback reaches a cache where there are outstanding MSHRs for the block, the packet is dropped. In the typical case though, the clean writeback allocates a block in the downstream cache, and marks it writable if the evicted block was writable. The patch changes the O3_ARM_v7a L1 cache configuration and the default L1 caches in config/common/Caches.py
2015-11-06mem: Add cache clusivityAndreas Hansson
This patch adds a parameter to control the cache clusivity, that is if the cache is mostly inclusive or exclusive. At the moment there is no intention to support strict policies, and thus the options are: 1) mostly inclusive, or 2) mostly exclusive. The choice of policy guides the behaviuor on a cache fill, and a new helper function, allocOnFill, is created to encapsulate the decision making process. For the timing mode, the decision is annotated on the MSHR on sending out the downstream packet, and in atomic we directly pass the decision to handleFill. We (ab)use the tempBlock in cases where we are not allocating on fill, leaving the rest of the cache unaffected. Simple and effective. This patch also makes it more explicit that multiple caches are allowed to consider a block writable (this is the case also before this patch). That is, for a mostly inclusive cache, multiple caches upstream may also consider the block exclusive. The caches considering the block writable/exclusive all appear along the same path to memory, and from a coherency protocol point of view it works due to the fact that we always snoop upwards in zero time before querying any downstream cache. Note that this patch does not introduce clean writebacks. Thus, for clean lines we are essentially removing a cache level if it is made mostly exclusive. For example, lines from the read-only L1 instruction cache or table-walker cache are always clean, and simply get dropped rather than being passed to the L2. If the L2 is mostly exclusive and does not allocate on fill it will thus never hold the line. A follow on patch adds the clean writebacks. The patch changes the L2 of the O3_ARM_v7a CPU configuration to be mostly exclusive (and stats are affected accordingly).
2015-11-06mem: Do not treat CleanEvict as a write operationAndreas Hansson
This patch changes the CleanEvict command type to not be considered a write. Initially it was made a zero-sized write to match the writeback command, but as things developed it became clear that it causes more problems than it solves. For example, the memory modules (and bridge) should not consider the CleanEvict as a write, but instead discard it. With this patch it will be neither a read, nor write, and as it does not need a response the slave will simply sink it.
2015-08-21mem: Add explicit Cache subclass and make BaseCache abstractAndreas Hansson
Open up for other subclasses to BaseCache and transition to using the explicit Cache subclass. --HG-- rename : src/mem/cache/BaseCache.py => src/mem/cache/Cache.py
2015-08-21mem: Move cache_impl.hh to cache.ccAndreas Hansson
There is no longer any need to keep the implementation in a header.
2015-07-30mem: Remove unused RequestCause in cacheAndreas Hansson
This patch removes the RequestCause, and also simplifies how we schedule the sending of packets through the memory-side port. The deassertion of bus requests is removed as it is not used.
2015-07-07sim: Decouple draining from the SimObject hierarchyAndreas Sandberg
Draining is currently done by traversing the SimObject graph and calling drain()/drainResume() on the SimObjects. This is not ideal when non-SimObjects (e.g., ports) need draining since this means that SimObjects owning those objects need to be aware of this. This changeset moves the responsibility for finding objects that need draining from SimObjects and the Python-side of the simulator to the DrainManager. The DrainManager now maintains a set of all objects that need draining. To reduce the overhead in classes owning non-SimObjects that need draining, objects inheriting from Drainable now automatically register with the DrainManager. If such an object is destroyed, it is automatically unregistered. This means that drain() and drainResume() should never be called directly on a Drainable object. While implementing the new functionality, the DrainManager has now been made thread safe. In practice, this means that it takes a lock whenever it manipulates the set of Drainable objects since SimObjects in different threads may create Drainable objects dynamically. Similarly, the drain counter is now an atomic_uint, which ensures that it is manipulated correctly when objects signal that they are done draining. A nice side effect of these changes is that it makes the drain state changes stricter, which the simulation scripts can exploit to avoid redundant drains.
2015-07-03mem: Remove redundant is_top_level cache parameterAndreas Hansson
This patch takes the final step in removing the is_top_level parameter from the cache. With the recent changes to read requests and write invalidations, the parameter is no longer needed, and consequently removed. This also means that asymmetric cache hierarchies are now fully supported (and we are actually using them already with L1 caches, but no table-walker caches, connected to a shared L2).
2015-07-03mem: Allow read-only caches and check complianceAndreas Hansson
This patch adds a parameter to the BaseCache to enable a read-only cache, for example for the instruction cache, or table-walker cache (not for x86). A number of checks are put in place in the code to ensure a read-only cache does not end up with dirty data. A follow-on patch adds suitable read requests to allow a read-only cache to explicitly ask for clean data.
2015-05-05mem: Snoop into caches on uncacheable accessesAndreas Hansson
This patch takes a last step in fixing issues related to uncacheable accesses. We do not separate uncacheable memory from uncacheable devices, and in cases where it is really memory, there are valid scenarios where we need to snoop since we do not support cache maintenance instructions (yet). On snooping an uncacheable access we thus provide data if possible. In essence this makes uncacheable accesses IO coherent. The snoop filter is also queried to steer the snoops, but not updated since the uncacheable accesses do not allocate a block.
2015-03-27mem: Remove redundant allocateUncachedReadBuffer in cacheAndreas Hansson
This patch removes the no-longer-needed allocateUncachedReadBuffer. Besides the checks it is exactly the same as allocateMissBuffer and thus provides no value.
2015-03-27mem: Align all MSHR entries to block boundariesAndreas Hansson
This patch aligns all MSHR queue entries to block boundaries to simplify checks for matches. Previously there were corner cases that could lead to existing entries not being identified as matches. There are, rather alarmingly, a few regressions that change with this patch.
2015-03-02mem: Tidy up the cache debug messagesAndreas Hansson
Avoid redundant inclusion of the name in the DPRINTF string.
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: Clarify usage of latency in the cacheMarco Balboni
This patch adds some much-needed clarity in the specification of the cache timing. For now, hit_latency and response_latency are kept as top-level parameters, but the cache itself has a number of local variables to better map the individual timing variables to different behaviours (and sub-components). The introduced variables are: - lookupLatency: latency of tag lookup, occuring on any access - forwardLatency: latency that occurs in case of outbound miss - fillLatency: latency to fill a cache block We keep the existing responseLatency The forwardLatency is used by allocateInternalBuffer() for: - MSHR allocateWriteBuffer (unchached write forwarded to WriteBuffer); - MSHR allocateMissBuffer (cacheable miss in MSHR queue); - MSHR allocateUncachedReadBuffer (unchached read allocated in MSHR queue) It is our assumption that the time for the above three buffers is the same. Similarly, for snoop responses passing through the cache we use forwardLatency.
2015-02-03mem: Clarify cache behaviour for pending dirty responsesAndreas Hansson
This patch adds a bit of clarification around the assumptions made in the cache when packets are sent out, and dirty responses are pending. As part of the change, the marking of an MSHR as in service is simplified slightly, and comments are added to explain what assumptions are made.
2014-12-02mem: Remove WriteInvalidate supportCurtis Dunham
Prepare for a different implementation following in the next patch
2014-06-27mem: write streaming support via WriteInvalidate promotionCurtis Dunham
Support full-block writes directly rather than requiring RMW: * a cache line is allocated in the cache upon receipt of a WriteInvalidateReq, not the WriteInvalidateResp. * only top-level caches allocate the line; the others just pass the request along and invalidate as necessary. * to close a timing window between the *Req and the *Resp, a new metadata bit tracks whether another cache has read a copy of the new line before the writeback to memory.
2014-09-03mem: Fix a bug in the cache port flow controlAndreas Hansson
This patch fixes a bug in the cache port where the retry flag was reset too early, allowing new requests to arrive before the retry was actually sent, but with the event already scheduled. This caused a deadlock in the interactions with the O3 LSQ. The patche fixes the underlying issue by shifting the resetting of the flag to be done by the event that also calls sendRetry(). The patch also tidies up the flow control in recvTimingReq and ensures that we also check if we already have a retry outstanding.
2014-01-24mem: Add support for a security bit in the memory systemGiacomo Gabrielli
This patch adds the basic building blocks required to support e.g. ARM TrustZone by discerning secure and non-secure memory accesses.
2014-01-24mem: track per-request latencies and access depths in the cache hierarchyMatt Horsnell
Add some values and methods to the request object to track the translation and access latency for a request and which level of the cache hierarchy responded to the request.
2013-02-15mem: Tighten up cache constness and scopingAndreas Hansson
This patch merely adopts a more strict use of const for the cache member functions and variables, and also moves a large portion of the member functions from public to protected.
2013-01-28cache: remove drainManager because it's not usedAnthony Gutierrez
the cache drainManager is set but never cleared, this is because the cache itself does not need to be drained and thus never triggers a signalDrainDone(). because the drainManager variable is not used properly and does not appear to be necessary it has been removed with this patch.
2012-11-02mem: Add support for writing back and flushing cachesAndreas Sandberg
This patch adds support for the following optional drain methods in the classical memory system's cache model: memWriteback() - Write back all dirty cache lines to memory using functional accesses. memInvalidate() - Invalidate all cache lines. Dirty cache lines are lost unless a writeback is requested. Since memWriteback() is called when checkpointing systems, this patch adds support for checkpointing systems with caches. The serialization code now checks whether there are any dirty lines in the cache. If there are dirty lines in the cache, the checkpoint is flagged as bad and a warning is printed.
2012-11-02sim: Move the draining interface into a separate base classAndreas Sandberg
This patch moves the draining interface from SimObject to a separate class that can be used by any object needing draining. However, objects not visible to the Python code (i.e., objects not deriving from SimObject) still depend on their parents informing them when to drain. This patch also gets rid of the CountedDrainEvent (which isn't really an event) and replaces it with a DrainManager.
2012-10-15Port: Add protocol-agnostic ports in the port hierarchyAndreas Hansson
This patch adds an additional level of ports in the inheritance hierarchy, separating out the protocol-specific and protocl-agnostic parts. All the functionality related to the binding of ports is now confined to use BaseMaster/BaseSlavePorts, and all the protocol-specific parts stay in the Master/SlavePort. In the future it will be possible to add other protocol-specific implementations. The functions used in the binding of ports, i.e. getMaster/SlavePort now use the base classes, and the index parameter is updated to use the PortID typedef with the symbolic InvalidPortID as the default.
2012-10-15Mem: Use cycles to express cache-related latenciesAndreas Hansson
This patch changes the cache-related latencies from an absolute time expressed in Ticks, to a number of cycles that can be scaled with the clock period of the caches. Ultimately this patch serves to enable future work that involves dynamic frequency scaling. As an immediate benefit it also makes it more convenient to specify cache performance without implicitly assuming a specific CPU core operating frequency. The stat blocked_cycles that actually counter in ticks is now updated to count in cycles. As the timing is now rounded to the clock edges of the cache, there are some regressions that change. Plenty of them have very minor changes, whereas some regressions with a short run-time are perturbed quite significantly. A follow-on patch updates all the statistics for the regressions.
2012-09-25Cache: add a response latency to the cachesMrinmoy Ghosh
In the current caches the hit latency is paid twice on a miss. This patch lets a configurable response latency be set of the cache for the backward path.
2012-08-22Port: Extend the QueuedPort interface and use where appropriateAndreas Hansson
This patch extends the queued port interfaces with methods for scheduling the transmission of a timing request/response. The methods are named similar to the corresponding sendTiming(Snoop)Req/Resp, replacing the "send" with "sched". As the queues are currently unbounded, the methods always succeed and hence do not return a value. This functionality was previously provided in the subclasses by calling PacketQueue::schedSendTiming with the appropriate parameters. With this change, there is no need to introduce these extra methods in the subclasses, and the use of the queued interface is more uniform and explicit.
2012-07-09Port: Move retry from port base class to Master/SlavePortAndreas Hansson
This patch is the last part of moving all protocol-related functionality out of the Port base class. All the send/recv functions are already moved, and the retry (which still governs all the timing transport functions) is the only part that remained in the base class. The only point where this currently causes a bit of inconvenience is in the bus where the retry list is global and holds Port pointers (not Master/SlavePort). This is about to change with the split into a request/response bus and will soon be removed anyway. The patch has no impact on any regressions.
2012-05-01MEM: Separate requests and responses for timing accessesAndreas Hansson
This patch moves send/recvTiming and send/recvTimingSnoop from the Port base class to the MasterPort and SlavePort, and also splits them into separate member functions for requests and responses: send/recvTimingReq, send/recvTimingResp, and send/recvTimingSnoopReq, send/recvTimingSnoopResp. A master port sends requests and receives responses, and also receives snoop requests and sends snoop responses. A slave port has the reciprocal behaviour as it receives requests and sends responses, and sends snoop requests and receives snoop responses. For all MemObjects that have only master ports or slave ports (but not both), e.g. a CPU, or a PIO device, this patch merely adds more clarity to what kind of access is taking place. For example, a CPU port used to call sendTiming, and will now call sendTimingReq. Similarly, a response previously came back through recvTiming, which is now recvTimingResp. For the modules that have both master and slave ports, e.g. the bus, the behaviour was previously relying on branches based on pkt->isRequest(), and this is now replaced with a direct call to the apprioriate member function depending on the type of access. Please note that send/recvRetry is still shared by all the timing accessors and remains in the Port base class for now (to maintain the current bus functionality and avoid changing the statistics of all regressions). The packet queue is split into a MasterPort and SlavePort version to facilitate the use of the new timing accessors. All uses of the PacketQueue are updated accordingly. With this patch, the type of packet (request or response) is now well defined for each type of access, and asserts on pkt->isRequest() and pkt->isResponse() are now moved to the appropriate send member functions. It is also worth noting that sendTimingSnoopReq no longer returns a boolean, as the semantics do not alow snoop requests to be rejected or stalled. All these assumptions are now excplicitly part of the port interface itself.
2012-04-14MEM: Separate snoops and normal memory requests/responsesAndreas Hansson
This patch introduces port access methods that separates snoop request/responses from normal memory request/responses. The differentiation is made for functional, atomic and timing accesses and builds on the introduction of master and slave ports. Before the introduction of this patch, the packets belonging to the different phases of the protocol (request -> [forwarded snoop request -> snoop response]* -> response) all use the same port access functions, even though the snoop packets flow in the opposite direction to the normal packet. That is, a coherent master sends normal request and receives responses, but receives snoop requests and sends snoop responses (vice versa for the slave). These two distinct phases now use different access functions, as described below. Starting with the functional access, a master sends a request to a slave through sendFunctional, and the request packet is turned into a response before the call returns. In a system without cache coherence, this is all that is needed from the functional interface. For the cache-coherent scenario, a slave also sends snoop requests to coherent masters through sendFunctionalSnoop, with responses returned within the same packet pointer. This is currently used by the bus and caches, and the LSQ of the O3 CPU. The send/recvFunctional and send/recvFunctionalSnoop are moved from the Port super class to the appropriate subclass. Atomic accesses follow the same flow as functional accesses, with request being sent from master to slave through sendAtomic. In the case of cache-coherent ports, a slave can send snoop requests to a master through sendAtomicSnoop. Just as for the functional access methods, the atomic send and receive member functions are moved to the appropriate subclasses. The timing access methods are different from the functional and atomic in that requests and responses are separated in time and send/recvTiming are used for both directions. Hence, a master uses sendTiming to send a request to a slave, and a slave uses sendTiming to send a response back to a master, at a later point in time. Snoop requests and responses travel in the opposite direction, similar to what happens in functional and atomic accesses. With the introduction of this patch, it is possible to determine the direction of packets in the bus, and no longer necessary to look for both a master and a slave port with the requested port id. In contrast to the normal recvFunctional, recvAtomic and recvTiming that are pure virtual functions, the recvFunctionalSnoop, recvAtomicSnoop and recvTimingSnoop have a default implementation that calls panic. This is to allow non-coherent master and slave ports to not implement these functions.
2012-03-30MEM: Introduce the master/slave port sub-classes in C++William Wang
This patch introduces the notion of a master and slave port in the C++ code, thus bringing the previous classification from the Python classes into the corresponding simulation objects and memory objects. The patch enables us to classify behaviours into the two bins and add assumptions and enfore compliance, also simplifying the two interfaces. As a starting point, isSnooping is confined to a master port, and getAddrRanges to slave ports. More of these specilisations are to come in later patches. The getPort function is not getMasterPort and getSlavePort, and returns a port reference rather than a pointer as NULL would never be a valid return value. The default implementation of these two functions is placed in MemObject, and calls fatal. The one drawback with this specific patch is that it requires some code duplication, e.g. QueuedPort becomes QueuedMasterPort and QueuedSlavePort, and BusPort becomes BusMasterPort and BusSlavePort (avoiding multiple inheritance). With the later introduction of the port interfaces, moving the functionality outside the port itself, a lot of the duplicated code will disappear again.
2012-03-22MEM: Split SimpleTimingPort into PacketQueue and portsAndreas Hansson
This patch decouples the queueing and the port interactions to simplify the introduction of the master and slave ports. By separating the queueing functionality from the port itself, it becomes much easier to distinguish between master and slave ports, and still retain the queueing ability for both (without code duplication). As part of the split into a PacketQueue and a port, there is now also a hierarchy of two port classes, QueuedPort and SimpleTimingPort. The QueuedPort is useful for ports that want to leave the packet transmission of outgoing packets to the queue and is used by both master and slave ports. The SimpleTimingPort inherits from the QueuedPort and adds the implemention of recvTiming and recvFunctional through recvAtomic. The PioPort and MessagePort are cleaned up as part of the changes. --HG-- rename : src/mem/tport.cc => src/mem/packet_queue.cc rename : src/mem/tport.hh => src/mem/packet_queue.hh
2012-03-09cache: Allow main memory to be at disjoint address ranges.Ali Saidi
2012-02-24MEM: Simplify cache ports preparing for master/slave splitAndreas Hansson
This patch splits the two cache ports into a master (memory-side) and slave (cpu-side) subclass of port with slightly different functionality. For example, it is only the CPU-side port that blocks incoming requests, and only the memory-side port that schedules send events outside of what the transmit list dictates. This patch simplifies the two classes by relying further on SimpleTimingPort and also generalises the latter to better accommodate the changes (introducing trySendTiming and scheduleSend). The memory-side cache port overrides sendDeferredPacket to be able to not only send responses from the transmit list, but also send requests based on the MSHRs. A follow on patch further simplifies the SimpleTimingPort and the cache ports.
2012-02-12mem: fix cache stats to use request ids correctlyDam Sunwoo
This patch fixes the cache stats to use the new request ids. Cache stats also display the requestor names in the vector subnames. Most cache stats now include "nozero" and "nonan" flags to reduce the amount of excessive cache stat dump. Also, simplified incMissCount()/incHitCount() functions.
2012-01-31Merge with head, hopefully the last time for this batch.Gabe Black
2012-01-31clang: Enable compiling gem5 using clang 2.9 and 3.0Koan-Sin Tan
This patch adds the necessary flags to the SConstruct and SConscript files for compiling using clang 2.9 and later (on Ubuntu et al and OSX XCode 4.2), and also cleans up a bunch of compiler warnings found by clang. Most of the warnings are related to hidden virtual functions, comparisons with unsigneds >= 0, and if-statements with empty bodies. A number of mismatches between struct and class are also fixed. clang 2.8 is not working as it has problems with class names that occur in multiple namespaces (e.g. Statistics in kernel_stats.hh). clang has a bug (http://llvm.org/bugs/show_bug.cgi?id=7247) which causes confusion between the container std::set and the function Packet::set, and this is currently addressed by not including the entire namespace std, but rather selecting e.g. "using std::vector" in the appropriate places.
2012-01-31MEM: Remove the otherPort from the cache portsAndreas Hansson
This patch is a very straight-forward simplification, removing the unecessary otherPort pointer from the cache port. The pointer was only used to forward range changes, and the address range is fixed for the cache. Removing the pointer simplifies the transition to master/slave ports.
2012-01-28Merge with the main repo.Gabe Black
--HG-- rename : src/mem/vport.hh => src/mem/fs_translating_port_proxy.hh rename : src/mem/translating_port.cc => src/mem/se_translating_port_proxy.cc rename : src/mem/translating_port.hh => src/mem/se_translating_port_proxy.hh
2012-01-17MEM: Separate queries for snooping and address rangesAndreas Hansson
This patch simplifies the address-range determination mechanism and also unifies the naming across ports and devices. It further splits the queries for determining if a port is snooping and what address ranges it responds to (aiming towards a separation of cache-maintenance ports and pure memory-mapped ports). Default behaviours are such that most ports do not have to define isSnooping, and master ports need not implement getAddrRanges.
2011-11-18SE/FS: Get rid of includes of config/full_system.hh.Gabe Black
2011-11-07SE/FS: Get rid of FULL_SYSTEM in mem.Gabe Black
2011-04-15trace: reimplement the DTRACE function so it doesn't use a vectorNathan Binkert
At the same time, rename the trace flags to debug flags since they have broader usage than simply tracing. This means that --trace-flags is now --debug-flags and --trace-help is now --debug-help
2011-04-15includes: sort all includesNathan Binkert