/*
- * Copyright (c) 2012-2013, 2015 ARM Limited
+ * Copyright (c) 2012-2013, 2015-2016, 2018 ARM Limited
* All rights reserved.
*
* The license below extends only to copyright in the software and shall
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Erik Hallnor
+ * Nikos Nikoleris
*/
/**
#ifndef __MEM_CACHE_MSHR_HH__
#define __MEM_CACHE_MSHR_HH__
+#include <cassert>
+#include <iosfwd>
#include <list>
+#include <string>
+#include <vector>
#include "base/printable.hh"
+#include "base/types.hh"
+#include "mem/cache/queue_entry.hh"
#include "mem/packet.hh"
+#include "mem/request.hh"
+#include "sim/core.hh"
-class CacheBlk;
-class MSHRQueue;
+class BaseCache;
/**
* Miss Status and handling Register. This class keeps all the information
* needed to handle a cache miss including a list of target requests.
* @sa \ref gem5MemorySystem "gem5 Memory System"
*/
-class MSHR : public Packet::SenderState, public Printable
+class MSHR : public QueueEntry, public Printable
{
/**
- * Consider the MSHRQueue a friend to avoid making everything public
+ * Consider the queues friends to avoid making everything public.
*/
+ template<typename Entry>
+ friend class Queue;
friend class MSHRQueue;
private:
- /** Cycle when ready to issue */
- Tick readyTime;
-
- /** True if the request is uncacheable */
- bool _isUncacheable;
-
/** Flag set by downstream caches */
bool downstreamPending;
- /** Will we have a dirty copy after this request? */
- bool pendingDirty;
+ /**
+ * Here we use one flag to track both if:
+ *
+ * 1. We are going to become owner or not, i.e., we will get the
+ * block in an ownership state (Owned or Modified) with BlkDirty
+ * set. This determines whether or not we are going to become the
+ * responder and ordering point for future requests that we snoop.
+ *
+ * 2. We know that we are going to get a writable block, i.e. we
+ * will get the block in writable state (Exclusive or Modified
+ * state) with BlkWritable set. That determines whether additional
+ * targets with needsWritable set will be able to be satisfied, or
+ * if not should be put on the deferred list to possibly wait for
+ * another request that does give us writable access.
+ *
+ * Condition 2 is actually just a shortcut that saves us from
+ * possibly building a deferred target list and calling
+ * promoteWritable() every time we get a writable block. Condition
+ * 1, tracking ownership, is what is important. However, we never
+ * receive ownership without marking the block dirty, and
+ * consequently use pendingModified to track both ownership and
+ * writability rather than having separate pendingDirty and
+ * pendingWritable flags.
+ */
+ bool pendingModified;
/** Did we snoop an invalidate while waiting for data? */
bool postInvalidate;
public:
- class Target {
+ /** Track if we sent this as a whole line write or not */
+ bool wasWholeLineWrite;
+
+ /** True if the entry is just a simple forward from an upper level */
+ bool isForward;
+
+ class Target : public QueueEntry::Target {
public:
enum Source {
FromPrefetcher
};
- Tick recvTime; //!< Time when request was received (for stats)
- Tick readyTime; //!< Time when request is ready to be serviced
- Counter order; //!< Global order (for memory consistency mgmt)
- PacketPtr pkt; //!< Pending request packet.
- Source source; //!< Did request come from cpu, memory, or prefetcher?
- bool markedPending; //!< Did we mark upstream MSHR
- //!< as downstreamPending?
+ const Source source; //!< Request from cpu, memory, or prefetcher?
+
+ /**
+ * We use this flag to track whether we have cleared the
+ * downstreamPending flag for the MSHR of the cache above
+ * where this packet originates from and guard noninitial
+ * attempts to clear it.
+ *
+ * The flag markedPending needs to be updated when the
+ * TargetList is in service which can be:
+ * 1) during the Target instantiation if the MSHR is in
+ * service and the target is not deferred,
+ * 2) when the MSHR becomes in service if the target is not
+ * deferred,
+ * 3) or when the TargetList is promoted (deferredTargets ->
+ * targets).
+ */
+ bool markedPending;
+
+ const bool allocOnFill; //!< Should the response servicing this
+ //!< target list allocate in the cache?
Target(PacketPtr _pkt, Tick _readyTime, Counter _order,
- Source _source, bool _markedPending)
- : recvTime(curTick()), readyTime(_readyTime), order(_order),
- pkt(_pkt), source(_source), markedPending(_markedPending)
+ Source _source, bool _markedPending, bool alloc_on_fill)
+ : QueueEntry::Target(_pkt, _readyTime, _order), source(_source),
+ markedPending(_markedPending), allocOnFill(alloc_on_fill)
{}
};
class TargetList : public std::list<Target> {
- /** Target list iterator. */
- typedef std::list<Target>::iterator Iterator;
- typedef std::list<Target>::const_iterator ConstIterator;
public:
- bool needsExclusive;
+ bool needsWritable;
bool hasUpgrade;
+ /** Set when the response should allocate on fill */
+ bool allocOnFill;
+ /**
+ * Determine whether there was at least one non-snooping
+ * target coming from another cache.
+ */
+ bool hasFromCache;
TargetList();
- void resetFlags() { needsExclusive = hasUpgrade = false; }
- bool isReset() { return !needsExclusive && !hasUpgrade; }
+
+ /**
+ * Use the provided packet and the source to update the
+ * flags of this TargetList.
+ *
+ * @param pkt Packet considered for the flag update
+ * @param source Indicates the source of the packet
+ * @param alloc_on_fill Whether the pkt would allocate on a fill
+ */
+ void updateFlags(PacketPtr pkt, Target::Source source,
+ bool alloc_on_fill);
+
+ /**
+ * Reset state
+ *
+ * @param blk_addr Address of the cache block
+ * @param blk_size Size of the cache block
+ */
+ void init(Addr blk_addr, Addr blk_size) {
+ blkAddr = blk_addr;
+ blkSize = blk_size;
+ writesBitmap.resize(blk_size);
+
+ resetFlags();
+ }
+
+ void resetFlags() {
+ canMergeWrites = true;
+ std::fill(writesBitmap.begin(), writesBitmap.end(), false);
+
+ needsWritable = false;
+ hasUpgrade = false;
+ allocOnFill = false;
+ hasFromCache = false;
+ }
+
+ /**
+ * Goes through the list of targets and uses them to populate
+ * the flags of this TargetList. When the function returns the
+ * flags are consistent with the properties of packets in the
+ * list.
+ */
+ void populateFlags();
+
+ /**
+ * Add the specified packet in the TargetList. This function
+ * stores information related to the added packet and updates
+ * accordingly the flags.
+ *
+ * @param pkt Packet considered for adding
+ */
+ void
+ updateWriteFlags(PacketPtr pkt)
+ {
+ // if we have already seen writes for the full block stop
+ // here, this might be a full line write followed by
+ // other compatible requests (e.g., reads)
+ if (!isWholeLineWrite()) {
+ // Avoid merging requests with special flags (e.g.,
+ // strictly ordered)
+ const Request::FlagsType no_merge_flags =
+ Request::UNCACHEABLE | Request::STRICT_ORDER |
+ Request::MMAPPED_IPR | Request::PRIVILEGED |
+ Request::LLSC | Request::MEM_SWAP |
+ Request::MEM_SWAP_COND | Request::SECURE;
+ const auto &req_flags = pkt->req->getFlags();
+ bool compat_write = pkt->isWrite() &&
+ !req_flags.isSet(no_merge_flags);
+ canMergeWrites &= compat_write;
+
+ // if this request is the first target in this list
+ // and additionally a whole-line write, we need to
+ // service it as a whole-line even if we won't allow
+ // any further merging (e.g., SECURE whole line
+ // write).
+ bool first_write = pkt->isWrite() && (size() == 0);
+ if (first_write || compat_write) {
+ auto offset = pkt->getOffset(blkSize);
+ auto begin = writesBitmap.begin() + offset;
+ std::fill(begin, begin + pkt->getSize(), true);
+ }
+ }
+ }
+
+ /**
+ * Tests if the flags of this TargetList have their default
+ * values.
+ *
+ * @return True if the TargetList are reset, false otherwise.
+ */
+ bool isReset() const {
+ return !needsWritable && !hasUpgrade && !allocOnFill &&
+ !hasFromCache && canMergeWrites;
+ }
+
+ /**
+ * Add the specified packet in the TargetList. This function
+ * stores information related to the added packet and updates
+ * accordingly the flags.
+ *
+ * @param pkt Packet considered for adding
+ * @param readTime Tick at which the packet is processed by this cache
+ * @param order A counter giving a unique id to each target
+ * @param source Indicates the source agent of the packet
+ * @param markPending Set for deferred targets or pending MSHRs
+ * @param alloc_on_fill Whether it should allocate on a fill
+ */
void add(PacketPtr pkt, Tick readyTime, Counter order,
- Target::Source source, bool markPending);
+ Target::Source source, bool markPending, bool alloc_on_fill);
+
+ /**
+ * Convert upgrades to the equivalent request if the cache line they
+ * refer to would have been invalid (Upgrade -> ReadEx, SC* -> Fail).
+ * Used to rejig ordering between targets waiting on an MSHR. */
void replaceUpgrades();
+
void clearDownstreamPending();
- bool checkFunctional(PacketPtr pkt);
+ void clearDownstreamPending(iterator begin, iterator end);
+ bool trySatisfyFunctional(PacketPtr pkt);
void print(std::ostream &os, int verbosity,
const std::string &prefix) const;
+
+ /**
+ * Check if this list contains writes that cover an entire
+ * cache line. This is used as part of the miss-packet
+ * creation. Note that new requests may arrive after a
+ * miss-packet has been created, and for the corresponding
+ * fill we use the wasWholeLineWrite field.
+ */
+ bool isWholeLineWrite() const
+ {
+ return std::all_of(writesBitmap.begin(), writesBitmap.end(),
+ [](bool i) { return i; });
+ }
+
+ private:
+ /** Address of the cache block for this list of targets. */
+ Addr blkAddr;
+
+ /** Size of the cache block. */
+ Addr blkSize;
+
+ /** Indicates whether we can merge incoming write requests */
+ bool canMergeWrites;
+
+ // NOTE: std::vector<bool> might not meet satisfy the
+ // ForwardIterator requirement and therefore cannot be used
+ // for writesBitmap.
+ /**
+ * Track which bytes are written by requests in this target
+ * list.
+ */
+ std::vector<char> writesBitmap;
};
/** A list of MSHRs. */
typedef std::list<MSHR *> List;
/** MSHR list iterator. */
typedef List::iterator Iterator;
- /** MSHR list const_iterator. */
- typedef List::const_iterator ConstIterator;
-
- /** Pointer to queue containing this MSHR. */
- MSHRQueue *queue;
-
- /** Order number assigned by the miss queue. */
- Counter order;
-
- /** Block aligned address of the MSHR. */
- Addr blkAddr;
-
- /** Block size of the cache. */
- unsigned blkSize;
-
- /** True if the request targets the secure memory space. */
- bool isSecure;
-
- /** True if the request has been sent to the bus. */
- bool inService;
-
- /** True if the request is just a simple forward from an upper level */
- bool isForward;
/** The pending* and post* flags are only valid if inService is
* true. Using the accessor functions lets us detect if these
* flags are accessed improperly.
*/
- /** True if we need to get an exclusive copy of the block. */
- bool needsExclusive() const { return targets.needsExclusive; }
+ /** True if we need to get a writable copy of the block. */
+ bool needsWritable() const { return targets.needsWritable; }
- bool isPendingDirty() const {
- assert(inService); return pendingDirty;
+ bool isCleaning() const {
+ PacketPtr pkt = targets.front().pkt;
+ return pkt->isClean();
+ }
+
+ bool isPendingModified() const {
+ assert(inService); return pendingModified;
}
bool hasPostInvalidate() const {
assert(inService); return postDowngrade;
}
- /** Thread number of the miss. */
- ThreadID threadNum;
+ bool sendPacket(BaseCache &cache) override;
- private:
+ bool allocOnFill() const {
+ return targets.allocOnFill;
+ }
+
+ /**
+ * Determine if there are non-deferred requests from other caches
+ *
+ * @return true if any of the targets is from another cache
+ */
+ bool hasFromCache() const {
+ return targets.hasFromCache;
+ }
- /** Data buffer (if needed). Currently used only for pending
- * upgrade handling. */
- uint8_t *data;
+ private:
+ /**
+ * Promotes deferred targets that satisfy a predicate
+ *
+ * Deferred targets are promoted to the target list if they
+ * satisfy a given condition. The operation stops at the first
+ * deferred target that doesn't satisfy the condition.
+ *
+ * @param pred A condition on a Target
+ */
+ void promoteIf(const std::function<bool (Target &)>& pred);
/**
* Pointer to this MSHR on the ready list.
TargetList deferredTargets;
public:
-
- bool isUncacheable() const { return _isUncacheable; }
+ /**
+ * Check if this MSHR contains only compatible writes, and if they
+ * span the entire cache line. This is used as part of the
+ * miss-packet creation. Note that new requests may arrive after a
+ * miss-packet has been created, and for the fill we therefore use
+ * the wasWholeLineWrite field.
+ */
+ bool isWholeLineWrite() const {
+ return targets.isWholeLineWrite();
+ }
/**
* Allocate a miss to this MSHR.
* @param pkt The original miss.
* @param when_ready When should the MSHR be ready to act upon.
* @param _order The logical order of this MSHR
+ * @param alloc_on_fill Should the cache allocate a block on fill
*/
void allocate(Addr blk_addr, unsigned blk_size, PacketPtr pkt,
- Tick when_ready, Counter _order);
+ Tick when_ready, Counter _order, bool alloc_on_fill);
- bool markInService(bool pending_dirty_resp);
+ void markInService(bool pending_modified_resp);
void clearDownstreamPending();
* Add a request to the list of targets.
* @param target The target.
*/
- void allocateTarget(PacketPtr target, Tick when, Counter order);
+ void allocateTarget(PacketPtr target, Tick when, Counter order,
+ bool alloc_on_fill);
bool handleSnoop(PacketPtr target, Counter order);
/** A simple constructor. */
int getNumTargets() const
{ return targets.size() + deferredTargets.size(); }
+ /**
+ * Extracts the subset of the targets that can be serviced given a
+ * received response. This function returns the targets list
+ * unless the response is a ReadRespWithInvalidate. The
+ * ReadRespWithInvalidate is only invalidating response that its
+ * invalidation was not expected when the request (a
+ * ReadSharedReq) was sent out. For ReadRespWithInvalidate we can
+ * safely service only the first FromCPU target and all FromSnoop
+ * targets (inform all snoopers that we no longer have the block).
+ *
+ * @param pkt The response from the downstream memory
+ */
+ TargetList extractServiceableTargets(PacketPtr pkt);
+
/**
* Returns true if there are targets left.
* @return true if there are targets
* Returns a reference to the first target.
* @return A pointer to the first target.
*/
- Target *getTarget()
+ QueueEntry::Target *getTarget() override
{
assert(hasTargets());
return &targets.front();
targets.pop_front();
}
- bool isForwardNoResponse() const
- {
- if (getNumTargets() != 1)
- return false;
- const Target *tgt = &targets.front();
- return tgt->source == Target::FromCPU && !tgt->pkt->needsResponse();
- }
-
bool promoteDeferredTargets();
- void handleFill(Packet *pkt, CacheBlk *blk);
+ /**
+ * Promotes deferred targets that do not require writable
+ *
+ * Move targets from the deferred targets list to the target list
+ * starting from the first deferred target until the first target
+ * that is a cache maintenance operation or needs a writable copy
+ * of the block
+ */
+ void promoteReadable();
- bool checkFunctional(PacketPtr pkt);
+ /**
+ * Promotes deferred targets that do not require writable
+ *
+ * Requests in the deferred target list are moved to the target
+ * list up until the first target that is a cache maintenance
+ * operation or needs a writable copy of the block
+ */
+ void promoteWritable();
+
+ bool trySatisfyFunctional(PacketPtr pkt);
+
+ /**
+ * Adds a delay relative to the current tick to the current MSHR
+ * @param delay_ticks the desired delay in ticks
+ */
+ void delay(Tick delay_ticks)
+ {
+ assert(readyTime <= curTick());
+ readyTime = curTick() + delay_ticks;
+ }
/**
* Prints the contents of this MSHR for debugging.
*/
void print(std::ostream &os,
int verbosity = 0,
- const std::string &prefix = "") const;
+ const std::string &prefix = "") const override;
/**
* A no-args wrapper of print(std::ostream...) meant to be
* invoked from DPRINTFs avoiding string overheads in fast mode
* @return string with mshr fields + [deferred]targets
*/
std::string print() const;
+
+ bool matchBlockAddr(const Addr addr, const bool is_secure) const override;
+ bool matchBlockAddr(const PacketPtr pkt) const override;
+ bool conflictAddr(const QueueEntry* entry) const override;
};
#endif // __MEM_CACHE_MSHR_HH__
projects / gem5.git / blobdiff