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2019-10-18mem: Delete the MessageReq and MessageResp memory commands.Gabe Black
Now that Message*Port is gone, there are no users of these two memory commands. They can now be deleted, simplifying the memory system slightly. Change-Id: If157dade4a3fb2610756c2ee81dc0c3fac670a26 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20824 Reviewed-by: Gabe Black <gabeblack@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Gabe Black <gabeblack@google.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-05-11cpu,mem: Add support for partial loads/stores and wide mem. accessesGiacomo Gabrielli
This changeset adds support for partial (or masked) loads/stores, i.e. loads/stores that can disable accesses to individual bytes within the target address range. In addition, this changeset extends the code to crack memory accesses across most CPU models (TimingSimpleCPU still TBD), so that arbitrarily wide memory accesses are supported. These changes are required for supporting ISAs with wide vectors. Additional authors: - Gabor Dozsa <gabor.dozsa@arm.com> - Tiago Muck <tiago.muck@arm.com> Change-Id: Ibad33541c258ad72925c0b1d5abc3e5e8bf92d92 Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/13518 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-04-28mem: Minimize the use of MemObject.Gabe Black
MemObject doesn't provide anything beyond its base ClockedObject any more, so this change removes it from most inheritance hierarchies. Occasionally MemObject is replaced with SimObject when I was fairly confident that the extra functionality of ClockedObject wasn't needed. Change-Id: Ic014ab61e56402e62548e8c831eb16e26523fdce Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18289 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com> Maintainer: Gabe Black <gabeblack@google.com>
2019-04-19mem: Add packet matching functionsDaniel R. Carvalho
Add both block and non-block-aligned packet matching functions, so that both address and secure bits are checked when checking whether a packet matches a request. Change-Id: Id0069befb925d112e06f250741cb47d9dfa249cc Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17533 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-04-19mem: Allow packet to provide its own addr rangeDaniel R. Carvalho
Add a getter to Packet to allow it to provide its own addr range. Change-Id: I2128ea3b71906502d10d9376b050a62407defd23 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17536 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-02-26mem-cache: Copy over flags to forwarded responseNikos Nikoleris
A cache that forwards a request to the memory below does not fill and forwards the response with the data to cache above. This change ensures that the flags of the original response are also preserved. Change-Id: I244b20b073c31b976358816c5b14bba413b8271f Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/16182 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
2018-10-26arch-arm: We add PRFM PST instruction for armyuetsu.kodama
Note current PRFM supports only PLD, but PST (prefetch for store) is also important for latency hiding. We also bug fix in disassembler to display prfop correctly. Change-Id: I9144e7233900aa2d555e1c1a6a2c2e41d837aa13 Signed-off-by: Yuetsu Kodama <yuetsu.kodama@riken.jp> Reviewed-on: https://gem5-review.googlesource.com/c/13675 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
2018-10-18mem: Restructure whole-line writes to simplify write mergingNikos Nikoleris
This patch changes how we deal with whole-line writes their responses. With these changes, we use the MSHR tracking to determine if a whole-line is written, and on a fill we simply handle the invalidation response, with the actual writes taking place as part of satisfying the CPU-side hit. Change-Id: I9a18e41a95db3c20b97f8bca7d95ff33d35a578b Reviewed-on: https://gem5-review.googlesource.com/c/12905 Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-10-18mem: Mark the guest endianness packet accessors as deprecated.Gabe Black
Change-Id: Iebefeb5b1ce905f2b45b30b7656d6a01d0724584 Reviewed-on: https://gem5-review.googlesource.com/c/13575 Maintainer: Gabe Black <gabeblack@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2018-10-18null: Stop specifying an endianness in isa_traits.hh.Gabe Black
The NULL ISA doesn't really have an endianness. Now that the packet accessors which consumed that endianness are gone, we can get rid of that setting as well. Change-Id: I8dd4c7b8236b07df4458fea377865f30141121d4 Reviewed-on: https://gem5-review.googlesource.com/c/13466 Reviewed-by: Gabe Black <gabeblack@google.com> Maintainer: Gabe Black <gabeblack@google.com>
2018-10-13mem: Get rid of some stray lines which ended up in packet.hh.Gabe Black
These were left in by mistake when refactoring patches for review. Change-Id: I4c39b5a3e2a2d3957e725a6ffcf48c25b8a69f2e Reviewed-on: https://gem5-review.googlesource.com/c/13495 Reviewed-by: Gabe Black <gabeblack@google.com> Maintainer: Gabe Black <gabeblack@google.com>
2018-10-12mem: Expose the raw packet accessor functions.Gabe Black
This avoids a place where data has its endianness switched so that when the endianness based accessors switch it back it returns to normal. It also makes it easier to show intent when accessing single bytes where endianness doesn't matter, and there's no contextual endianness. Change-Id: I1b97396c1b9bb39727d35112d90e3969e5fe0aab Reviewed-on: https://gem5-review.googlesource.com/c/13455 Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-09-07mem: Add a QoS-aware Memory Controller typeMatteo Andreozzi
This is the implementation of QoS algorithms support for gem5 memory objects. This change-list provides a framework for specifying QoS algorithm which can be used to prioritise service to specific masters in the memory controller. The QoS support implemented here is designed to be extendable so that new QoS algorithms can be easily plugged into the memory controller as "QoS Policies". Change-Id: I0b611f13fce54dd1dd444eb806f8e98afd248bd5 Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-on: https://gem5-review.googlesource.com/11970 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-07-23mem: Rename Packet::checkFunctional to trySatisfyFunctionalRobert Kovacsics
Packet::checkFunctional also wrote data to/from the packet depending on if it was read/write, respectively, which the 'check' in the name would suggest otherwise. This renames it to doFunctional, which is more suggestive. It also renames any function called checkFunctional which calls Packet::checkFunctional. These are - Bridge::BridgeMasterPort::checkFunctional - calls Packet::checkFunctional - MSHR::checkFunctional - calls Packet::checkFunctional - MSHR::TargetList::checkFunctional - calls Packet::checkFunctional - Queue<>::checkFunctional (of src/mem/cache/queue.hh, not src/cpu/minor/buffers.h) - Instantiated with Queue<WriteQueueEntry> and Queue<MSHR> - WriteQueueEntry - calls Packet::checkFunctional - WriteQueueEntry::TargetList - calls Packet::checkFunctional - MemDelay::checkFunctional - calls QueuedSlavePort/QueuedMasterPort::checkFunctional - Packet::checkFunctional - PacketQueue::checkFunctional - calls Packet::checkFunctional - QueuedSlavePort::checkFunctional - calls PacketQueue::doFunctional - QueuedMasterPort::checkFunctional - calls PacketQueue::doFunctional - SerialLink::SerialLinkMasterPort::checkFunctional - calls Packet::doFunctional Change-Id: Ieca2579c020c329040da053ba8e25820801b62c5 Reviewed-on: https://gem5-review.googlesource.com/11810 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2018-06-14base,mem: Support AtomicOpFunctor in the classic memory systemTuan Ta
AtomicOpFunctor can be used to implement atomic memory operations. AtomicOpFunctor is captured inside a memory request and executed directly in the memory hierarchy in a single step. This patch enables AtomicOpFunctor pointers to be included in a memory request and executed in a single step in the classic cache system. This patch also makes the copy constructor of Request class do a deep copy of AtomicOpFunctor object. This prevents a copy of a Request object from accessing a deleted AtomicOpFunctor object. Change-Id: I6649532b37f711e55f4552ad26893efeb300dd37 Reviewed-on: https://gem5-review.googlesource.com/8185 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-06-11misc: Using smart pointers for memory RequestsGiacomo Travaglini
This patch is changing the underlying type for RequestPtr from Request* to shared_ptr<Request>. Having memory requests being managed by smart pointers will simplify the code; it will also prevent memory leakage and dangling pointers. Change-Id: I7749af38a11ac8eb4d53d8df1252951e0890fde3 Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/10996 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-04-17mem: Add a helper function to get a word of variable lengthAndreas Sandberg
There are many devices that need to handle reads/writes of different word sizes. A common pattern is a switch statement that check for the size of a packet and then calls the corresponding Packet::(get|set)<uintXX_t> methods. Simplify this by implementing Packet::(get|set)UintX helper functions. The getter reads a word of the size specified in the packet and the specified endianness. The word is then zero-extended to 64 bits. Conversely, the setter truncates the word down to the size required in the packet and then byte-swaps it to the desired endianness. Change-Id: I2f0c27fe3903abf3859bea13b07c7f5f0fb0809f Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/9761 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2018-04-05mem-cache: Use Packet functions to write data blocksDaniel R. Carvalho
Instead of using raw memcpy, use the proper writer functions from the Packet class in Cache. Fixed typos in comments of these functions. Change-Id: I156a00989c6cbaa73763349006a37a18243d6ed4 Reviewed-on: https://gem5-review.googlesource.com/9661 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2017-12-05mem: Co-ordination of CMOs in the xbarNikos Nikoleris
A clean packet request serving a cache maintenance operation (CMO) visits all memories down to the specified xbar. The visited caches invalidate their copy (if the CMO is invalidating) and if a dirty copy is found a write packet writes the dirty data to the memory level below the specified xbar. A response is send back when all the caches are clean and/or invalidated and the specified xbar has seen the write packet. This patch adds the following functionality in the xbar: 1) Accounts for the cache clean requests that go through the xbar 2) Generates the cache clean response when both the cache clean request and the corresponding writeclean packet has crossed the destination xbar. Previously transactions in the xbar were identified using the pointer of the original request. Cache clean transactions comprise of two different packets, the clean request and the writeclean, and therefore have different request pointers. This patch adds support for custom transaction IDs that by default take the value of the request pointer but can be overriden by the contructor. This allows the clean request and writeclean share the same id which the coherent xbar uses to co-ordinate them and send the response in a timely manner. Change-Id: I80db76386a1caded38dc66e6e18f930c3bb800ff Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com> Reviewed-on: https://gem5-review.googlesource.com/5051 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2017-12-05mem: Add support for CMOs in the cacheNikos Nikoleris
This change adds support for maintenance operations (CMOs) in the cache. The supported memory operations clean and/or invalidate a cache block as specified by its VA to the specified xbar (PoU, PoC). A cache maintenance packet visits all memories down to the specified xbar. Caches need to invalidate their copy if it is an invalidating CMO. If it is (additionally) a cleaning CMO and a dirty copy exists, the cache cleans it with a WriteClean request. Change-Id: Ibf31daa7213925898f3408738b11b1dd76c90b79 Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com> Reviewed-on: https://gem5-review.googlesource.com/5049 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2017-12-05mem: Add support for cache maintenance operation requestsNikos Nikoleris
This change adds new packet cmds and request flags for cache maintenance operations. 1) A cache clean operation writes dirty data in the first memory below the specified xbar and updates any old copies in the memories above it. 2) A cache invalidate operation invalidates all copies of the specified block in the memories above the specified xbar 3) A clean and invalidate operation is a combination of the two operations above Change-Id: If45702848bdd568de532cd57cba58499e5e4354c Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Curtis Dunham <curtis.dunham@arm.com> Reviewed-by: Anouk Van Laer <anouk.vanlaer@arm.com> Reviewed-on: https://gem5-review.googlesource.com/5047 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2017-12-05mem: Support for specifying the destination of a WriteCleanNikos Nikoleris
Previously, WriteClean packets would always write to the first memory below unless the memory was unable to allocate in which case it would be forwarded further below. This change adds support for specifying the destination of a WriteClean packet. The cache annotates the request with the specified destination and marks the packet as write-through upon its creation. The coherent xbar checks packets for their destination and resets the write-through flag when necessary e.g., the coherent xbar that is set as the PoC will reset the write-through flag for packets to the PoC. Change-Id: I84b653f5cb6e46e97e09508649a3725d72d94606 Reviewed-by: Curtis Dunham <curtis.dunham@arm.com> Reviewed-by: Anouk Van Laer <anouk.vanlaer@arm.com> Reviewed-on: https://gem5-review.googlesource.com/5046 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2017-12-05mem: Add a WriteClean command to the packet classNikos Nikoleris
A WriteClean packet allows a cache to write a block to a memory below without evicting its copy. A typical usecase for a WriteClean packet is a cache clean operation. Change-Id: If356cb067da5ddf3210c135f41ef0891fb811568 Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Curtis Dunham <curtis.dunham@arm.com> Reviewed-by: Anouk Van Laer <anouk.vanlaer@arm.com> Reviewed-on: https://gem5-review.googlesource.com/5044 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2017-12-04misc: Rename misc.(hh|cc) to logging.(hh|cc)Gabe Black
These files aren't a collection of miscellaneous stuff, they're the definition of the Logger interface, and a few utility macros for calling into that interface (panic, warn, etc.). Change-Id: I84267ac3f45896a83c0ef027f8f19c5e9a5667d1 Reviewed-on: https://gem5-review.googlesource.com/6226 Reviewed-by: Brandon Potter <Brandon.Potter@amd.com> Maintainer: Gabe Black <gabeblack@google.com>
2016-12-05mem: Assert that the responderHadWritable is set only onceNikos Nikoleris
Change-Id: Ie3beeef25331f84a0a5bcc17f7a791f4a829695b Reviewed-by: Andreas Hansson <andreas.hansson@arm.com> Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
2016-08-12mem: Add a FromCache packet attributeAndreas Hansson
This patch adds a FromCache attribute to the packet, and updates a number of the existing request commands to reflect that the request originates from a cache. The attribute simplifies checking if a requests came from a cache or not, and this is used by both the cache and snoop filter in follow-on patches. Change-Id: Ib0a7a080bbe4d6036ddd84b46fd45bc7eb41cd8f Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Tony Gutierrez <anthony.gutierrez@amd.com> Reviewed-by: Steve Reinhardt <stever@gmail.com>
2016-01-19* * *Tony Gutierrez
mem: support for gpu-style RMWs in ruby This patch adds support for GPU-style read-modify-write (RMW) operations in ruby. Such atomic operations are traditionally executed at the memory controller (instead of through an L1 cache using cache-line locking). Currently, this patch works by propogating operation functors through the memory system.
2016-01-11scons: Enable -Wextra by defaultAndreas Hansson
Make best use of the compiler, and enable -Wextra as well as -Wall. There are a few issues that had to be resolved, but they are all trivial.
2015-12-31mem: Do not rely on the NeedsWritable flag for responsesAndreas Hansson
This patch removes the NeedsWritable flag for all responses, as it is really only the request that needs a writable response. The response, on the other hand, should in these cases always provide the line in a writable state, as indicated by the hasSharers flag not being set. When we send requests that has NeedsWritable set, the response will always have the hasSharers flag not set. Additionally, there are cases where the request did not have NeedsWritable set, and we still get a writable response with the hasSharers flag not set. This never happens on snoops, but is used by downstream caches to pass ownership upstream. As part of this patch, the affected response types are updated, and the snoop filter is similarly modified to check only the hasSharers flag (as it should). A sanity check is also added to the packet class, asserting that we never look at the NeedsWritable flag for responses. No regressions are affected.
2015-12-31mem: Do not allocate space for packet data if not neededAndreas Hansson
This patch looks at the request and response command to determine if either actually has any data payload, and if not, we do not allocate any space for packet data. The only tricky case is where the command type is changed as part of the MSHR functionality. In these cases where the original packet had no data, but the new packet does, we need to explicitly call allocate().
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.
2015-12-09mem: remove acq/rel cmds from packet and add mem fence reqTony Gutierrez
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
2015-09-25mem: Make the coherent crossbar account for timing snoopsAndreas Hansson
This patch introduces the concept of a snoop latency. Given the requirement to snoop and forward packets in zero time (due to the coherency mechanism), the latency is accounted for later. On a snoop, we establish the latency, and later add it to the header delay of the packet. To allow multiple caches to contribute to the snoop latency, we use a separate variable in the packet, and then take the maximum before adding it to the header delay.
2015-08-24mem: Revert requirement on packet addr/size always validAndreas Hansson
This patch reverts part of (842f56345a42), as apparently there are use-cases outside the main repository relying on the late setting of the physical address.
2015-08-21mem: Reflect that packet address and size are always validAndreas Hansson
This patch simplifies the packet, and removes the possibility of creating a packet without a valid address and/or size. Under no circumstances are these fields set at a later point, and thus they really have to be provided at construction time. The patch also fixes a case there the MinorCPU creates a packet without a valid address and size, only to later delete it.
2015-08-07mem: Cleanup packet accessor methodsAndreas Sandberg
The Packet::get() and Packet::set() methods both have very strange semantics. Currently, they automatically convert between the guest system's endianness and the host system's endianness. This behavior is usually undesired and unexpected. This patch introduces three new method pairs to access data: * getLE() / setLE() - Get data stored as little endian. * getBE() / setBE() - Get data stored as big endian. * get(ByteOrder) / set(v, ByteOrder) - Configurable endianness For example, a little endian device that is receiving a write request will use teh getLE() method to get the data from the packet. The old interface will be deprecated once all existing devices have been ported to the new interface.
2015-08-07mem: Remove extraneous acquire/release flags and attributesAndreas Hansson
This patch removes the extraneous flags and attributes from the request and packet, and simply leaves the new commands. The change introduced when adding acquire/release breaks all compatibility with existing traces, and there is really no need for any new flags and attributes. The commands should be sufficient. This patch fixes packet tracing (urgent), and also removes the unnecessary complexity.
2015-07-20mem: add request types for acquire and releaseDavid Hashe
Add support for acquire and release requests. These synchronization operations are commonly supported by several modern instruction sets.
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 packetAndreas Hansson
Some minor fixes and removal of dead code. Changing the flags to be enums rather than static const (to avoid any linking issues caused by the latter). Also adding a getBlockAddr member which hopefully can slowly finds its way into caches, snoop filters etc.
2015-07-04mem: packet: Add const to constructor argumentNilay Vaish
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: 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: Add check for express snoop in packet destructorAli Jafri
Snoop packets share the request pointer with the originating packets. We need to ensure that the snoop packet destruction does not delete the request. Snoops are used for reads, invalidations, HardPFReqs, Writebacks and CleansEvicts. Reads, invalidations, and HardPFReqs need a response so their snoops do not delete the request. For Writebacks and CleanEvicts we need to check explicitly for whethere the current packet is an express snoop, in whcih case do not delete the request.
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.
2015-02-11mem: restructure Packet cmd initialization a bit moreSteve Reinhardt
Refactor the way that specific MemCmd values are generated for packets. The new approach is a little more elegant in that we assign the right value up front, and it's also more amenable to non-heap-allocated Packet objects. Also replaced the code in the Minor model that was still doing it the ad-hoc way. This is basically a refinement of http://repo.gem5.org/gem5/rev/711eb0e64249.
2015-03-02mem: Add byte mask to Packet::checkFunctionalAndreas Hansson
This patch changes the valid-bytes start/end to a proper byte mask. With the changes in timing introduced in previous patches there are more packets waiting in queues, and there are regressions using the checker CPU failing due to non-contigous read data being found in the various cache queues. This patch also adds some more comments explaining what is going on, and adds the fourth and missing case to Packet::checkFunctional.
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.
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