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/**
* Copyright (c) 2018 Metempsy Technology Consulting
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Javier Bueno
*/
/**
* Implementation of the Irregular Stream Buffer prefetcher
* Reference:
* Jain, A., & Lin, C. (2013, December). Linearizing irregular memory
* accesses for improved correlated prefetching. In Proceedings of the
* 46th Annual IEEE/ACM International Symposium on Microarchitecture
* (pp. 247-259). ACM.
*/
#ifndef __MEM_CACHE_PREFETCH_IRREGULAR_STREAM_BUFFER_HH__
#define __MEM_CACHE_PREFETCH_IRREGULAR_STREAM_BUFFER_HH__
#include "base/callback.hh"
#include "base/sat_counter.hh"
#include "mem/cache/prefetch/associative_set.hh"
#include "mem/cache/prefetch/queued.hh"
struct IrregularStreamBufferPrefetcherParams;
class IrregularStreamBufferPrefetcher : public QueuedPrefetcher
{
/** Size in bytes of a temporal stream */
const size_t chunkSize;
/** Number of prefetch candidates per Physical-to-Structural entry */
const unsigned prefetchCandidatesPerEntry;
/** Number of maximum prefetches requests created when predicting */
const unsigned degree;
/**
* Training Unit Entry datatype, it holds the last accessed address and
* its secure flag
*/
struct TrainingUnitEntry : public TaggedEntry {
Addr lastAddress;
bool lastAddressSecure;
};
/** Map of PCs to Training unit entries */
AssociativeSet<TrainingUnitEntry> trainingUnit;
/** Address Mapping entry, holds an address and a confidence counter */
struct AddressMapping {
Addr address;
SatCounter counter;
AddressMapping(unsigned bits) : address(0), counter(bits)
{}
};
/**
* Maps a set of contiguous addresses to another set of (not necessarily
* contiguos) addresses, with their corresponding confidence counters
*/
struct AddressMappingEntry : public TaggedEntry {
std::vector<AddressMapping> mappings;
AddressMappingEntry(size_t num_mappings, unsigned counter_bits)
: mappings(num_mappings, counter_bits)
{}
void reset() override
{
for (auto &entry : mappings) {
entry.address = 0;
entry.counter.reset();
}
}
};
/** Physical-to-Structured mappings table */
AssociativeSet<AddressMappingEntry> psAddressMappingCache;
/** Structured-to-Physical mappings table */
AssociativeSet<AddressMappingEntry> spAddressMappingCache;
/**
* Counter of allocated structural addresses, increased by "chunkSize",
* each time a new structured address is allocated
*/
uint64_t structuralAddressCounter;
/**
* Add a mapping to the Structured-to-Physica mapping table
* @param structuralAddress structural address
* @param is_secure whether this page is inside the secure memory area
* @param physical_address corresponding physical address
*/
void addStructuralToPhysicalEntry(Addr structuralAddress, bool is_secure,
Addr physical_address);
/**
* Obtain the Physical-to-Structured mapping entry of the given physical
* address. If the entry does not exist a new one is allocated, replacing
* an existing one if needed.
* @param paddr physical address
* @param is_secure whether this page is inside the secure memory area
* @result reference to the entry
*/
AddressMapping& getPSMapping(Addr paddr, bool is_secure);
public:
IrregularStreamBufferPrefetcher(
const IrregularStreamBufferPrefetcherParams *p);
~IrregularStreamBufferPrefetcher() {}
void calculatePrefetch(const PrefetchInfo &pfi,
std::vector<AddrPriority> &addresses) override;
};
#endif//__MEM_CACHE_PREFETCH_IRREGULAR_STREAM_BUFFER_HH__
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