summaryrefslogtreecommitdiff
path: root/src/mem/cache
AgeCommit message (Collapse)Author
2015-09-04mem: Avoid setting markPending if not neededAndreas Hansson
In cases where a newly added target does not have any upstream MSHR to mark as downstreamPending, remember that nothing is marked. This allows us to avoid attempting to find the MSHR as part of the clearing of downstreamPending.
2015-09-04mem: Tidy up CacheSetAndreas Hansson
Minor tweaks and house keeping.
2015-09-04mem: Tidy up the snoop state-transition logicAndreas Hansson
Remove broken and unused option to pass dirty data on non-exclusive snoops. Also beef up the comments a bit.
2015-08-21arm, mem: Remove unused CLEAR_LL request flagAndreas Hansson
Cleaning up dead code. The CLREX stores zero directly to MISCREG_LOCKFLAG and so the request flag is no longer needed. The corresponding functionality in the cache tags is also removed.
2015-08-21mem: Remove unused cache squash functionalityAndreas Hansson
Tidying up.
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.
2015-08-07base: Declare a type for context IDsAndreas Sandberg
Context IDs used to be declared as ad hoc (usually as int). This changeset introduces a typedef for ContextIDs and a constant for invalid context IDs.
2015-07-30mem: Add missing clean eviction on uncacheable accessAndreas Hansson
This patch adds a missing clean eviction, occuring when an uncacheable access flushes and invalidates an existing block.
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.
2015-07-30mem: Make caches way awareDavid Guillen-Fandos
This patch makes cache sets aware of the way number. This enables some nice features such as the ablity to restrict way allocation. The implemented mechanism allows to set a maximum way number to be allocated 'k' which must fulfill 0 < k <= N (where N is the number of ways). In the future more sophisticated mechasims can be implemented.
2015-07-30mem: Transition away from isSupplyExclusive for writebacksAndreas Hansson
This patch changes how writebacks communicate whether the line is passed as modified or owned. Previously we relied on the isSupplyExclusive mechanism, which was originally designed to avoid unecessary snoops. For normal cache requests we use the sharedAsserted mechanism to determine if a block should be marked writeable or not, and with this patch we transition the writebacks to also use this mechanism. Conceptually this is cleaner and more consistent.
2015-07-30mem: Tidy up CacheBlk classAndreas Hansson
This patch modernises and tidies up the CacheBlk, removing dead code.
2015-07-13mem: Fix (ab)use of emplace to avoid temporary object creationAndreas Hansson
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.
2015-07-07sim: 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.
2015-07-07sim: Make the drain state a global typed enumAndreas Sandberg
The drain state enum is currently a part of the Drainable interface. The same state machine will be used by the DrainManager to identify the global state of the simulator. Make the drain state a global typed enum to better cater for this usage scenario.
2015-07-07sim: Refactor the serialization base classAndreas Sandberg
Objects that are can be serialized are supposed to inherit from the Serializable class. This class is meant to provide a unified API for such objects. However, so far it has mainly been used by SimObjects due to some fundamental design limitations. This changeset redesigns to the serialization interface to make it more generic and hide the underlying checkpoint storage. Specifically: * Add a set of APIs to serialize into a subsection of the current object. Previously, objects that needed this functionality would use ad-hoc solutions using nameOut() and section name generation. In the new world, an object that implements the interface has the methods serializeSection() and unserializeSection() that serialize into a named /subsection/ of the current object. Calling serialize() serializes an object into the current section. * Move the name() method from Serializable to SimObject as it is no longer needed for serialization. The fully qualified section name is generated by the main serialization code on the fly as objects serialize sub-objects. * Add a scoped ScopedCheckpointSection helper class. Some objects need to serialize data structures, that are not deriving from Serializable, into subsections. Previously, this was done using nameOut() and manual section name generation. To simplify this, this changeset introduces a ScopedCheckpointSection() helper class. When this class is instantiated, it adds a new /subsection/ and subsequent serialization calls during the lifetime of this helper class happen inside this section (or a subsection in case of nested sections). * The serialize() call is now const which prevents accidental state manipulation during serialization. Objects that rely on modifying state can use the serializeOld() call instead. The default implementation simply calls serialize(). Note: The old-style calls need to be explicitly called using the serializeOld()/serializeSectionOld() style APIs. These are used by default when serializing SimObjects. * Both the input and output checkpoints now use their own named types. This hides underlying checkpoint implementation from objects that need checkpointing and makes it easier to change the underlying checkpoint storage code.
2015-07-03mem: Delay responses in the crossbar before forwardingAndreas 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.
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: Split WriteInvalidateReq into write and invalidateAndreas Hansson
WriteInvalidateReq ensures that a whole-line write does not incur the cost of first doing a read exclusive, only to later overwrite the data. This patch splits the existing WriteInvalidateReq into a WriteLineReq, which is done locally, and an InvalidateReq that is sent out throughout the memory system. The WriteLineReq re-uses the normal WriteResp. The change allows us to better express the difference between the cache that is performing the write, and the ones that are merely invalidating. As a consequence, we no longer have to rely on the isTopLevel flag. Moreover, the actual memory in the system does not see the intitial write, only the writeback. We were marking the written line as dirty already, so there is really no need to also push the write all the way to the memory. The overall flow of the write-invalidate operation remains the same, i.e. the operation is only carried out once the response for the invalidate comes back. This patch adds the InvalidateResp for this very reason.
2015-07-03mem: Add ReadCleanReq and ReadSharedReq packetsAndreas Hansson
This patch adds two new read requests packets: ReadCleanReq - For a cache to explicitly request clean data. The response is thus exclusive or shared, but not owned or modified. The read-only caches (see previous patch) use this request type to ensure they do not get dirty data. ReadSharedReq - We add this to distinguish cache read requests from those issued by other masters, such as devices and CPUs. Thus, devices use ReadReq, and caches use ReadCleanReq, ReadExReq, or ReadSharedReq. For the latter, the response can be any state, shared, exclusive, owned or even modified. Both ReadCleanReq and ReadSharedReq re-use the normal ReadResp. The two transactions are aligned with the emerging cache-coherent TLM standard and the AMBA nomenclature. With this change, the normal ReadReq should never be used by a cache, and is reserved for the actual (non-caching) masters in the system. We thus have a way of identifying if a request came from a cache or not. The introduction of ReadSharedReq thus removes the need for the current isTopLevel hack, and also allows us to stop relying on checking the packet size to determine if the source is a cache or not. This is fixed in follow-on patches.
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.
2015-07-03mem: Add clean evicts to improve snoop filter trackingAli Jafri
This patch adds eviction notices to the caches, to provide accurate tracking of cache blocks in snoop filters. We add the CleanEvict message to the memory heirarchy and use both CleanEvicts and Writebacks with BLOCK_CACHED flags to propagate notice of clean and dirty evictions respectively, down the memory hierarchy. Note that the BLOCK_CACHED flag indicates whether there exist any copies of the evicted block in the caches above the evicting cache. The purpose of the CleanEvict message is to notify snoop filters of silent evictions in the relevant caches. The CleanEvict message behaves much like a Writeback. CleanEvict is a write and a request but unlike a Writeback, CleanEvict does not have data and does not need exclusive access to the block. The cache generates the CleanEvict message on a fill resulting in eviction of a clean block. Before travelling downwards CleanEvict requests generate zero-time snoop requests to check if the same block is cached in upper levels of the memory heirarchy. If the block exists, the cache discards the CleanEvict message. The snoops check the tags, writeback queue and the MSHRs of upper level caches in a manner similar to snoops generated from HardPFReqs. Currently CleanEvicts keep travelling towards main memory unless they encounter the block corresponding to their address or reach main memory (since we have no well defined point of serialisation). Main memory simply discards CleanEvict messages. We have modified the behavior of Writebacks, such that they generate snoops to check for the presence of blocks in upper level caches. It is possible in our current implmentation for a lower level cache to be writing back a block while a shared copy of the same block exists in the upper level cache. If the snoops find the same block in upper level caches, we set the BLOCK_CACHED flag in the Writeback message. We have also added logic to account for interaction of other message types with CleanEvicts waiting in the writeback queue. A simple example is of a response arriving at a cache removing any CleanEvicts to the same address from the cache's writeback queue.
2015-06-09mem: Fix snoop packet data allocation bugAndreas Hansson
This patch fixes an issue where the snoop packet did not properly forward the data pointer in case of static data.
2015-03-17mem: Create a request copy for deferred snoopsStephan Diestelhorst
Sometimes, we need to defer an express snoop in an MSHR, but the original request might complete and deallocate the original pkt->req. In those cases, create a copy of the request so that someone who is inspecting the delayed snoop can also inspect the request still. All of this is rather hacky, but the allocation / linking and general life-time management of Packet and Request is rather tricky. Deleting the copy is another tricky area, testing so far has shown that the right copy is deleted at the right time.
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.
2015-05-05mem: Pass shared downstream through cachesAndreas Hansson
This patch ensures that we pass on information about a packet being shared (rather than exclusive), when forwarding a packet downstream. Without this patch there is a risk that a downstream cache considers the line exclusive when it really isn't.
2015-05-05mem: Add forward snoop check for HardPFReqsAli Jafri
We should always check whether the cache is supposed to be forwarding snoops before generating snoops.
2015-05-05mem: Add missing stats update for uncacheable MSHRsAndreas Hansson
This patch adds a missing counter update for the uncacheable accesses. By updating this counter we also get a meaningful average latency for uncacheable accesses (previously inf).
2015-05-05mem: Tidy up BaseCache parametersAndreas Hansson
This patch simply tidies up the BaseCache parameters and removes the unused "two_queue" parameter.
2015-05-05mem: Remove templates in cache modelDavid Guillen
This patch changes the cache implementation to rely on virtual methods rather than using the replacement policy as a template argument. There is no impact on the simulation performance, and overall the changes make it easier to modify (and subclass) the cache and/or replacement policy.
2015-03-27mem: Support any number of master-IDs in stride prefetcherStephan Diestelhorst
The stride prefetcher had a hardcoded number of contexts (i.e. master-IDs) that it could handle. Since master IDs need to be unique per system, and every core, cache etc. requires a separate master port, a static limit on these does not make much sense. Instead, this patch adds a small hash map that will map all master IDs to the right prefetch state and dynamically allocates new state for new master IDs.
2015-03-27mem: Allocate cache writebacks before new MSHRsAndreas Hansson
This patch changes the order of writeback allocation such that any writebacks resulting from a tag lookup (e.g. for an uncacheable access), are added to the writebuffer before any new MSHR entries are allocated. This ensures that the writebacks logically precedes the new allocations. The patch also changes the uncacheable flush to use proper timed (or atomic) writebacks, as opposed to functional writes.
2015-03-27mem: Cleanup flow for uncacheable accessesAndreas Hansson
This patch simplifies the code dealing with uncacheable timing accesses, aiming to align it with the existing miss handling. Similar to what we do in atomic, a timing request now goes through Cache::access (where the block is also flushed), and then proceeds to ignore any existing MSHR for the block in question. This unifies the flow for cacheable and uncacheable accesses, and for atomic and timing.
2015-03-27mem: Ignore uncacheable MSHRs when finding matchesAndreas Hansson
This patch changes how we search for matching MSHRs, ignoring any MSHR that is allocated for an uncacheable access. By doing so, this patch fixes a corner case in the MSHRs where incorrect data ended up being copied into a (cacheable) read packet due to a first uncacheable MSHR target of size 4, followed by a cacheable target to the same MSHR of size 64. The latter target was filled with nonsense data.
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: Modernise MSHR iterators to C++11Andreas Hansson
This patch updates the iterators in the MSHR and MSHR queues to use C++11 range-based for loops. It also does a bit of additional house keeping.
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.
2015-03-27mem: Rename PREFETCH_SNOOP_SQUASH flag to BLOCK_CACHEDAli Jafri
This patch subsumes the PREFETCH_SNOOP_SQUASH flag with the more generic BLOCK_CACHED flag. Future patches implementing cache eviction messages can use the BLOCK_CACHED flag in almost the same manner as hardware prefetches use the PREFETCH_SNOOP_SQUASH flag. The PREFTECH_SNOOP_FLAG is set if the prefetch target is found in the tags or the MSHRs in any state, so we are simply replacing calls to setPrefetchSquashed() with setBlockCached(). The case of where the prefetch target is found in the writeback MSHRs of upper level caches continues to be covered by the MEM_INHIBIT flag.
2015-03-19mem: Use emplace front/back for deferred packetsAndreas Hansson
Embrace C++11 for the deferred packets as we actually store the objects in the data structure, and not just pointers.
2015-02-11mem: remove redundant test in in Cache::recvTimingResp()Steve Reinhardt
For some reason we were checking mshr->hasTargets() even though we had already called mshr->getTarget() unconditionally earlier in the same function (which asserts if there are no targets). Get rid of this useless check, and while we're at it get rid of the redundant call to mshr->getTarget(), since we still have the value saved in a local var.
2015-02-11mem: add local var in Cache::recvTimingResp()Steve Reinhardt
The main loop in recvTimingResp() uses target->pkt all over the place. Create a local tgt_pkt to help keep lines under the line length limit.
2015-03-14mem: clean up write buffer check in Cache::handleSnoop()Steve Reinhardt
The 'if (writebacks.size)' check was redundant, because writeBuffer.findMatches() would return false if the writebacks list was empty. Also renamed 'mshr' to 'wb_entry' in this context since we are pointing at a writebuffer entry and not an MSHR (even though it's the same C++ class).
2015-03-02mem: Unify all cache DPRINTF address formattingAndreas Hansson
This patch changes all the DPRINTF messages in the cache to use '%#llx' every time a packet address is printed. The inclusion of '#' ensures '0x' is prepended, and since the address type is a uint64_t %x really should be %llx.
2015-03-02mem: Fix cache MSHR conflict determinationAndreas Hansson
This patch fixes a rather subtle issue in the sending of MSHR requests in the cache, where the logic previously did not check for conflicts between the MSRH queue and the write queue when requests were not ready. The correct thing to do is to always check, since not having a ready MSHR does not guarantee that there is no conflict. The underlying problem seems to have slipped past due to the symmetric timings used for the write queue and MSHR queue. However, with the recent timing changes the bug caused regressions to fail.
2015-03-02mem: Add option to force in-order insertion in PacketQueueStephan Diestelhorst
By default, the packet queue is ordered by the ticks of the to-be-sent packages. With the recent modifications of packages sinking their header time when their resposne leaves the caches, there could be cases of MSHR targets being allocated and ordered A, B, but their responses being sent out in the order B,A. This led to inconsistencies in bus traffic, in particular the snoop filter observing first a ReadExResp and later a ReadRespWithInv. Logically, these were ordered the other way around behind the MSHR, but due to the timing adjustments when inserting into the PacketQueue, they were sent out in the wrong order on the bus, confusing the snoop filter. This patch adds a flag (off by default) such that these special cases can request in-order insertion into the packet queue, which might offset timing slighty. This is expected to occur rarely and not affect timing results.
2015-03-02mem: Downstream components consumes new crossbar delaysMarco Balboni
This patch makes the caches and memory controllers consume the delay that is annotated to a packet by the crossbar. Previously many components simply threw these delays away. Note that the devices still do not pay for these delays.
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.