summaryrefslogtreecommitdiff
path: root/src/mem/cache/mshr.hh
AgeCommit message (Collapse)Author
2018-03-21mem-cache: Allow clean operations when block allocation failsNikos Nikoleris
Block allocation can fail when there is an in-service MSHR that operates on the victim block. This can happed due to: * an upgrade operation: a request that needs a writable copy of the block finds a shared (non-writable) copy of the block in the cache and has allocates an MSHR for the pending upgrade operation, or * a clean operation: a clean request finds a dirty copy of the block and allocates an MSHR for the pending clean operation. This changes relaxes an assertion to allow for the 2nd case (cache clean operations). Change-Id: Ib51482160b5f2b3702ed744b0eac2029d34bc9d4 Reviewed-by: Curtis Dunham <curtis.dunham@arm.com> Reviewed-on: https://gem5-review.googlesource.com/9021 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Gabe Black <gabeblack@google.com>
2016-12-05mem: Service only the 1st FromCPU MSHR target on ReadRespWithInvNikos Nikoleris
A response to a ReadReq can either be a ReadResp or a ReadRespWithInvalidate. As we add targets to an MSHR for a ReadReq we assume that the response will be a ReadResp. When the response is invalidating (ReadRespWithInvalidate) servicing more than one targets can potentially violate the memory ordering. This change fixes the way we handle a ReadRespWithInvalidate. When a cache receives a ReadRespWithInvalidate we service only the first FromCPU target and all the FromSnoop targets from the MSHR target list. The rest of the FromCPU targets are deferred and serviced by a new request. Change-Id: I75c30c268851987ee5f8644acb46f440b4eeeec2 Reviewed-by: Andreas Hansson <andreas.hansson@arm.com> Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
2016-12-05mem: Keep track of allocOnFill in the TargetListNikos Nikoleris
Previously the information of whether a response was allocating or not was a property of the MSHR. This change makes this flag a property of the TargetList. Differernt TargetLists, e.g. the targets and the deferred targets lists might have different values. Additionally, the information about whether each of the target expects an allocating response is stored inside the TargetList container. This allows for repopulating the flag in case some of the targets are removed. Change-Id: If3ec2516992f42a6d9da907009ffe3ab8d0d2021 Reviewed-by: Andreas Hansson <andreas.hansson@arm.com> Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
2016-12-05mem: Add support for repopulating the flags of an MSHR TargetListNikos Nikoleris
This patch adds support for repopulating the flags of an MSHR TargetList. The added functionality makes it possible to remove targets from a TargetList without leaving it in an inconsistent state. Change-Id: I3f7a8e97bfd3e2e49bebad056d11bbfb087aad91 Reviewed-by: Andreas Hansson <andreas.hansson@arm.com> Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
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.
2015-08-10mem, cpu: Add assertions to snoop invalidation logicStephan Diestelhorst
This patch adds assertions that enforce that only invalidating snoops will ever reach into the logic that tracks in-order load completion and also invalidation of LL/SC (and MONITOR / MWAIT) monitors. Also adds some comments to MSHR::replaceUpgrades().
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.
2015-12-28mem: Remove unused cache squash functionalityAndreas Hansson
This patch removes the unused squash function from the MSHR queue, and the associated (and also unused) threadNum member from the MSHR.
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).
2015-10-29mem: Clarify cache MSHR handling on fillAndreas Hansson
This patch addresses the upgrading of deferred targets in the MSHR, and makes it clearer by explicitly calling out what is happening (deferred targets are promoted if we get exclusivity without asking for it).
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.
2015-02-03mem: 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
2014-10-21mem: don't inhibit WriteInv's or defer snoops on their MSHRsCurtis Dunham
WriteInvalidate semantics depend on the unconditional writeback or they won't complete. Also, there's no point in deferring snoops on their MSHRs, as they don't get new data at the end of their life cycle the way other transactions do. Add comment in the cache about a minor inefficiency re: WriteInvalidate.
2014-10-29mem: have WriteInvalidate obsolete MSHRsCurtis Dunham
Since WriteInvalidate directly writes into the cache, it can create tricky timing interleavings with reads and writes to the same cache line that haven't yet completed. This patch ensures that these requests, when completed, don't overwrite the newer data from the WriteInvalidate.
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.
2013-05-30mem: Spring cleaning of MSHR and MSHRQueueAndreas Hansson
This patch does some minor tidying up of the MSHR and MSHRQueue. The clean up started as part of some ad-hoc tracing and debugging, but seems worthwhile enough to go in as a separate patch. The highlights of the changes are reduced scoping (private) members where possible, avoiding redundant new/delete, and constructor initialisation to please static code analyzers.
2013-04-22mem: Adding verbose debug output in the memory systemUri Wiener
This patch provides useful printouts throughut the memory system. This includes pretty-printed cache tags and function call messages (call-stack like).
2012-09-25MEM: Put memory system document into doxygenDjordje Kovacevic
2011-01-07Replace curTick global variable with accessor functions.Steve Reinhardt
This step makes it easy to replace the accessor functions (which still access a global variable) with ones that access per-thread curTick values.
2010-09-09cache: coherence protocol enhancements & bug fixesSteve Reinhardt
Allow lower-level caches (e.g., L2 or L3) to pass exclusive copies to higher levels (e.g., L1). This eliminates a lot of unnecessary upgrade transactions on read-write sequences to non-shared data. Also some cleanup of MSHR coherence handling and multiple bug fixes.
2009-06-04types: clean up types, especially signed vs unsignedNathan Binkert
2009-05-26types: add a type for thread IDs and try to use it everywhereNathan Binkert
2009-02-16Fixes to get prefetching working again.Steve Reinhardt
Apparently we broke it with the cache rewrite and never noticed. Thanks to Bao Yungang <baoyungang@gmail.com> for a significant part of these changes (and for inspiring me to work on the rest). Some other overdue cleanup on the prefetch code too.
2008-11-10Cache: Refactor packet forwarding a bit.Steve Reinhardt
Makes adding write-through operations easier.
2008-02-10Rename cache files for brevity and consistency with rest of tree.Steve Reinhardt
--HG-- rename : src/mem/cache/base_cache.cc => src/mem/cache/base.cc rename : src/mem/cache/base_cache.hh => src/mem/cache/base.hh rename : src/mem/cache/cache_blk.cc => src/mem/cache/blk.cc rename : src/mem/cache/cache_blk.hh => src/mem/cache/blk.hh rename : src/mem/cache/cache_builder.cc => src/mem/cache/builder.cc rename : src/mem/cache/miss/mshr.cc => src/mem/cache/mshr.cc rename : src/mem/cache/miss/mshr.hh => src/mem/cache/mshr.hh rename : src/mem/cache/miss/mshr_queue.cc => src/mem/cache/mshr_queue.cc rename : src/mem/cache/miss/mshr_queue.hh => src/mem/cache/mshr_queue.hh rename : src/mem/cache/prefetch/base_prefetcher.cc => src/mem/cache/prefetch/base.cc rename : src/mem/cache/prefetch/base_prefetcher.hh => src/mem/cache/prefetch/base.hh rename : src/mem/cache/prefetch/ghb_prefetcher.cc => src/mem/cache/prefetch/ghb.cc rename : src/mem/cache/prefetch/ghb_prefetcher.hh => src/mem/cache/prefetch/ghb.hh rename : src/mem/cache/prefetch/stride_prefetcher.cc => src/mem/cache/prefetch/stride.cc rename : src/mem/cache/prefetch/stride_prefetcher.hh => src/mem/cache/prefetch/stride.hh rename : src/mem/cache/prefetch/tagged_prefetcher.cc => src/mem/cache/prefetch/tagged.cc rename : src/mem/cache/prefetch/tagged_prefetcher.hh => src/mem/cache/prefetch/tagged.hh rename : src/mem/cache/tags/base_tags.cc => src/mem/cache/tags/base.cc rename : src/mem/cache/tags/base_tags.hh => src/mem/cache/tags/base.hh rename : src/mem/cache/tags/Repl.py => src/mem/cache/tags/iic_repl/Repl.py rename : src/mem/cache/tags/repl/gen.cc => src/mem/cache/tags/iic_repl/gen.cc rename : src/mem/cache/tags/repl/gen.hh => src/mem/cache/tags/iic_repl/gen.hh rename : src/mem/cache/tags/repl/repl.hh => src/mem/cache/tags/iic_repl/repl.hh extra : convert_revision : ff7a35cc155a8d80317563c45cebe405984eac62