From: Daniel R. Carvalho Date: Wed, 30 May 2018 12:31:06 +0000 (+0200) Subject: mem-cache: Create CPack compressor X-Git-Tag: v19.0.0.0~730 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=28059ffcdf50871b1be573c29a656da9473287d1;p=gem5.git mem-cache: Create CPack compressor Implementation of C-Pack, as described in "C-Pack: A High- Performance Microprocessor Cache Compression Algorithm". C-Pack uses pattern matching schemes to detect and compress frequently appearing data patterns. As in the original paper, it divides the input in 32-bit words, and uses 6 patterns to match with its dictionary. For the patterns, each letter represents a byte: Z is a null byte, M is a dictionary match, X is a new value. The patterns are ZZZZ, XXXX, MMMM, MMXX, ZZZX, MMMX. Change-Id: I2efc9db2c862620dcc1155300e39be558f9017e0 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11105 Maintainer: Nikos Nikoleris Reviewed-by: Nikos Nikoleris Tested-by: kokoro --- diff --git a/src/mem/cache/compressors/Compressors.py b/src/mem/cache/compressors/Compressors.py index 1d9de1980..b266ccc95 100644 --- a/src/mem/cache/compressors/Compressors.py +++ b/src/mem/cache/compressors/Compressors.py @@ -45,3 +45,8 @@ class BDI(BaseCacheCompressor): use_more_compressors = Param.Bool(True, "True if should use all possible" \ "combinations of base and delta for the compressors. False if using" \ "only the lowest possible delta size for each base size."); + +class CPack(BaseCacheCompressor): + type = 'CPack' + cxx_class = 'CPack' + cxx_header = "mem/cache/compressors/cpack.hh" diff --git a/src/mem/cache/compressors/SConscript b/src/mem/cache/compressors/SConscript index 38ce34082..0b3ba6451 100644 --- a/src/mem/cache/compressors/SConscript +++ b/src/mem/cache/compressors/SConscript @@ -34,3 +34,4 @@ SimObject('Compressors.py') Source('base.cc') Source('bdi.cc') +Source('cpack.cc') diff --git a/src/mem/cache/compressors/cpack.cc b/src/mem/cache/compressors/cpack.cc new file mode 100644 index 000000000..1192963e2 --- /dev/null +++ b/src/mem/cache/compressors/cpack.cc @@ -0,0 +1,227 @@ +/* + * Copyright (c) 2018 Inria + * 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: Daniel Carvalho + */ + +/** @file + * Implementation of the CPack cache compressor. + */ + +#include "mem/cache/compressors/cpack.hh" + +#include +#include + +#include "debug/CacheComp.hh" +#include "params/CPack.hh" + +CPack::CompData::CompData(const std::size_t dictionary_size) + : CompressionData() +{ +} + +CPack::CompData::~CompData() +{ +} + +CPack::CPack(const Params *p) + : BaseCacheCompressor(p), dictionarySize(2*blkSize/8) +{ + dictionary.resize(dictionarySize); + + resetDictionary(); +} + +void +CPack::resetDictionary() +{ + // Reset number of valid entries + numEntries = 0; + + // Set all entries as 0 + std::array zero_word = {0, 0, 0, 0}; + std::fill(dictionary.begin(), dictionary.end(), zero_word); +} + +std::unique_ptr +CPack::compressWord(const uint32_t data) +{ + // Split data in bytes + const std::array bytes = { + static_cast(data & 0xFF), + static_cast((data >> 8) & 0xFF), + static_cast((data >> 16) & 0xFF), + static_cast((data >> 24) & 0xFF) + }; + + // Start as a no-match pattern. A negative match location is used so that + // patterns that depend on the dictionary entry don't match + std::unique_ptr pattern = + PatternFactory::getPattern(bytes, {0, 0, 0, 0}, -1); + + // Search for word on dictionary + for (std::size_t i = 0; i < numEntries; i++) { + // Try matching input with possible patterns + std::unique_ptr temp_pattern = + PatternFactory::getPattern(bytes, dictionary[i], i); + + // Check if found pattern is better than previous + if (temp_pattern->getSizeBits() < pattern->getSizeBits()) { + pattern = std::move(temp_pattern); + } + } + + // Update stats + patternStats[pattern->getPatternNumber()]++; + + // Push into dictionary + if ((numEntries < dictionarySize) && pattern->shouldAllocate()) { + dictionary[numEntries++] = bytes; + } + + return pattern; +} + +std::unique_ptr +CPack::compress(const uint64_t* data, Cycles& comp_lat, Cycles& decomp_lat) +{ + std::unique_ptr comp_data = + std::unique_ptr(new CompData(dictionarySize)); + + // Compression size + std::size_t size = 0; + + // Reset dictionary + resetDictionary(); + + // Compress every word sequentially + for (std::size_t i = 0; i < blkSize/8; i++) { + const uint32_t first_word = ((data[i])&0xFFFFFFFF00000000) >> 32; + const uint32_t second_word = (data[i])&0x00000000FFFFFFFF; + + // Compress both words + std::unique_ptr first_pattern = compressWord(first_word); + std::unique_ptr second_pattern = compressWord(second_word); + + // Update total line compression size + size += first_pattern->getSizeBits() + second_pattern->getSizeBits(); + + // Print debug information + DPRINTF(CacheComp, "Compressed %08x to %s\n", first_word, + first_pattern->print()); + DPRINTF(CacheComp, "Compressed %08x to %s\n", second_word, + second_pattern->print()); + + // Append to pattern list + comp_data->entries.push_back(std::move(first_pattern)); + comp_data->entries.push_back(std::move(second_pattern)); + } + + // Set final compression size + comp_data->setSizeBits(size); + + // Set compression latency (Accounts for pattern matching, length + // generation, packaging and shifting) + comp_lat = Cycles(blkSize/8+5); + + // Set decompression latency (1 qword per cycle) + decomp_lat = Cycles(blkSize/8); + + // Return compressed line + return std::move(comp_data); +} + +uint32_t +CPack::decompressWord(const Pattern* pattern) +{ + std::array data; + + // Search for matching entry + std::vector>::iterator entry_it = + dictionary.begin(); + std::advance(entry_it, pattern->getMatchLocation()); + + // Decompress the match. If the decompressed value must be added to + // the dictionary, do it + if (pattern->decompress(*entry_it, data)) { + dictionary[numEntries++] = data; + } + + // Return word + return (((((data[3] << 8) | data[2]) << 8) | data[1]) << 8) | data[0]; +} + +void +CPack::decompress(const CompressionData* comp_data, uint64_t* data) +{ + const CompData* cpack_comp_data = static_cast(comp_data); + + // Reset dictionary + resetDictionary(); + + // Decompress every entry sequentially + std::vector decomp_words; + for (const auto& entry : cpack_comp_data->entries) { + const uint32_t word = decompressWord(&*entry); + decomp_words.push_back(word); + + // Print debug information + DPRINTF(CacheComp, "Decompressed %s to %x\n", entry->print(), word); + } + + // Concatenate the decompressed words to generate the cache lines + for (std::size_t i = 0; i < blkSize/8; i++) { + data[i] = (static_cast(decomp_words[2*i]) << 32) | + decomp_words[2*i+1]; + } +} + +void +CPack::regStats() +{ + BaseCacheCompressor::regStats(); + + // We store the frequency of each pattern + patternStats + .init(Pattern::getNumPatterns()) + .name(name() + ".pattern") + .desc("Number of data entries that were compressed to this pattern.") + ; + + for (unsigned i = 0; i < Pattern::getNumPatterns(); ++i) { + patternStats.subname(i, Pattern::getName(i)); + patternStats.subdesc(i, "Number of data entries that match pattern " + + Pattern::getName(i)); + } +} + +CPack* +CPackParams::create() +{ + return new CPack(this); +} diff --git a/src/mem/cache/compressors/cpack.hh b/src/mem/cache/compressors/cpack.hh new file mode 100644 index 000000000..664a37601 --- /dev/null +++ b/src/mem/cache/compressors/cpack.hh @@ -0,0 +1,551 @@ +/* + * Copyright (c) 2018 Inria + * 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: Daniel Carvalho + */ + +/** @file + * Definition of CPack compression, from "C-Pack: A High-Performance + * Microprocessor Cache Compression Algorithm". + * + * The dictionary is composed of 32-bit entries. + * + * The patterns are implemented as individual classes that have a checking + * function isPattern(), to determine if the data fits the pattern, and a + * decompress() function, which decompresses the contents of a pattern. + * Every new pattern must inherit from the Pattern class and be added to the + * patternFactory. + */ + +#ifndef __MEM_CACHE_COMPRESSORS_CPACK_HH__ +#define __MEM_CACHE_COMPRESSORS_CPACK_HH__ + +#include +#include +#include +#include +#include + +#include "base/types.hh" +#include "mem/cache/compressors/base.hh" + +struct CPackParams; + +class CPack : public BaseCacheCompressor +{ + private: + /** + * Compression data for CPack. It consists of a vector of patterns. + */ + class CompData; + + // Forward declaration of all possible patterns + class Pattern; + class PatternZZZZ; + class PatternXXXX; + class PatternMMMM; + class PatternMMXX; + class PatternZZZX; + class PatternMMMX; + + /** + * Create a factory to determine if input matches a pattern. The if else + * chains are constructed by recursion. The patterns should be explored + * sorted by size for correct behaviour. + */ + template + struct Factory + { + static std::unique_ptr getPattern( + const std::array& bytes, + const std::array& dict_bytes, const int match_location) + { + // If match this pattern, instantiate it. If a negative match + // location is used, the patterns that use the dictionary bytes + // must return false. This is used when there are no dictionary + // entries yet + if (Head::isPattern(bytes, dict_bytes, match_location)) { + return std::unique_ptr( + new Head(bytes, match_location)); + // Otherwise, go for next pattern + } else { + return Factory::getPattern(bytes, dict_bytes, + match_location); + } + } + }; + + /** + * Specialization to end the recursion. + */ + template + struct Factory + { + static std::unique_ptr getPattern( + const std::array& bytes, + const std::array& dict_bytes, const int match_location) + { + // Instantiate last pattern. Should be the XXXX pattern. + return std::unique_ptr(new Head(bytes, match_location)); + } + }; + + /** + * Convenience factory declaration. The templates must be organized by + * size, with the smallest first, and "no-match" last. + */ + using PatternFactory = Factory; + + /** + * The dictionary. + */ + std::vector> dictionary; + + /** + * Dictionary size. + */ + const std::size_t dictionarySize; + + /** + * Number of valid entries in the dictionary. + */ + std::size_t numEntries; + + /** + * @defgroup CompressionStats Compression specific statistics. + * @{ + */ + + /** + * Number of data entries that were compressed to each pattern. + */ + Stats::Vector patternStats; + + /** + * @} + */ + + /** + * Compress data. + * + * @param data Data to be compressed. + * @return The pattern this data matches. + */ + std::unique_ptr compressWord(const uint32_t data); + + /** + * Decompress a word. + * + * @param pattern The pattern to be decompressed. + * @return The decompressed word. + */ + uint32_t decompressWord(const Pattern* pattern); + + /** + * Clear all dictionary entries. + */ + void resetDictionary(); + + /** + * Apply compression. + * + * @param data The cache line to be compressed. + * @param comp_lat Compression latency in number of cycles. + * @param decomp_lat Decompression latency in number of cycles. + * @return Cache line after compression. + */ + std::unique_ptr compress( + const uint64_t* data, Cycles& comp_lat, Cycles& decomp_lat) override; + + /** + * Decompress data. + * + * @param comp_data Compressed cache line. + * @param data The cache line to be decompressed. + */ + void decompress(const CompressionData* comp_data, uint64_t* data) override; + + public: + /** Convenience typedef. */ + typedef CPackParams Params; + + /** + * Default constructor. + */ + CPack(const Params *p); + + /** + * Default destructor. + */ + ~CPack() {}; + + /** + * Register local statistics. + */ + void regStats() override; +}; + +/** + * The compressed data is composed of multiple pattern entries. To add a new + * pattern one should inherit from this class and implement isPattern() and + * decompress. Then the new pattern must be added to the PatternFactory + * declaration in crescent order of size (in the CPack class). The pattern + * must be also added to the Name enum in the CPack::Pattern class before + * NUM_PATTERNS. + */ +class CPack::Pattern +{ + protected: + + /** + * The patterns proposed in the paper. Each letter represents a byte: + * Z is a null byte, M is a dictionary match, X is a new value. + * These are used as indexes to reference the pattern data. If a new + * pattern is added, it must be done before NUM_PATTERNS. + */ + typedef enum { + ZZZZ, XXXX, MMMM, MMXX, ZZZX, MMMX, NUM_PATTERNS + } PatternNumber; + + /** + * Pattern enum number. + */ + const PatternNumber patternNumber; + + /** + * Code associated to the pattern. + */ + const uint8_t code; + + /** + * Length, in bits, of the code and match location. + */ + const uint8_t length; + + /** + * Number of unmatched bytes; + */ + const uint8_t numUnmatchedBytes; + + /** + * Index representing the the match location. + */ + const int matchLocation; + + /** + * Wether the pattern allocates a dictionary entry or not. + */ + const bool allocate; + + /** + * Get code of this pattern. + * + * @return The code. + */ + uint8_t getCode() const { return code; } + + public: + /** + * Default constructor. + * + * @param number Pattern number. + * @param code Code associated to this pattern. + * @param metadata_length Length, in bits, of the code and match location. + * @param num_unmatched_bytes Number of unmatched bytes. + * @param match_location Index of the match location. + */ + Pattern(const PatternNumber number, const uint64_t code, + const uint64_t metadata_length, const uint64_t num_unmatched_bytes, + const int match_location, const bool allocate = true) + : patternNumber(number), code(code), length(metadata_length), + numUnmatchedBytes(num_unmatched_bytes), + matchLocation(match_location), allocate(allocate) {}; + + /** + * Default destructor. + */ + virtual ~Pattern() = default; + + /** + * Trick function to get the number of patterns. + * + * @return The number of defined patterns. + */ + static uint64_t getNumPatterns() { return NUM_PATTERNS; }; + + /** + * Get enum number associated to this pattern. + * + * @return The pattern enum number. + */ + PatternNumber getPatternNumber() const { return patternNumber; }; + + /** + * Get meta-name assigned to the given pattern. + * + * @param number The number of the pattern. + * @return The meta-name of the pattern. + */ + static std::string getName(int number) + { + static std::map patternNames = { + {ZZZZ, "ZZZZ"}, {XXXX, "XXXX"}, {MMMM, "MMMM"}, + {MMXX, "MMXX"}, {ZZZX, "ZZZX"}, {MMMX, "MMMX"} + }; + + return patternNames[(PatternNumber)number]; + }; + + /** + * Get the index of the dictionary match location. + * + * @return The index of the match location. + */ + uint8_t getMatchLocation() const { return matchLocation; } + + /** + * Get size, in bits, of the pattern (excluding prefix). Corresponds to + * unmatched_data_size + code_length. + * + * @return The size. + */ + std::size_t getSizeBits() const { + return numUnmatchedBytes*CHAR_BIT + length; + } + + /** + * Determine if pattern allocates a dictionary entry. + * + * @return True if should allocate a dictionary entry. + */ + bool shouldAllocate() const { + return allocate; + } + + std::string print() const { + return csprintf("pattern %s (encoding %x, size %u bits)", + getName(patternNumber), getCode(), getSizeBits()); + } + + /** + * Decompress the pattern. Each pattern has its own way of interpreting + * its data. + * + * @param dict_bytes The bytes in the corresponding matching entry. + * @param data The decompressed pattern. + * @return Whether entry should be added to dictionary or not. + */ + virtual bool decompress(const std::array dict_bytes, + std::array& data) const = 0; +}; + +class CPack::PatternZZZZ : public Pattern +{ + public: + PatternZZZZ(const std::array bytes, const int match_location) + : Pattern(ZZZZ, 0x0, 2, 0, 0, false) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + return (bytes[3] == 0) && (bytes[2] == 0) && (bytes[1] == 0) && + (bytes[0] == 0); + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = {0, 0, 0, 0}; + return false; + } +}; + +class CPack::PatternXXXX : public Pattern +{ + private: + /** + * A copy of the word. + */ + const std::array bytes; + + public: + PatternXXXX(const std::array bytes, const int match_location) + : Pattern(XXXX, 0x1, 2, 4, 0, true), bytes(bytes) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + // It can always be an unmatch, as it is set to this class when other + // patterns fail + return true; + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = bytes; + return true; + } +}; + +class CPack::PatternMMMM : public Pattern +{ + public: + PatternMMMM(const std::array bytes, const int match_location) + : Pattern(MMMM, 0x2, 6, 0, match_location, true) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + return (bytes == dict_bytes) && (match_location >= 0); + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = dict_bytes; + return true; + } +}; + +class CPack::PatternMMXX : public Pattern +{ + private: + /** + * A copy of the unmatched bytes. + */ + const uint8_t byte0; + const uint8_t byte1; + + public: + PatternMMXX(const std::array bytes, const int match_location) + : Pattern(MMXX, 0xC, 8, 2, match_location, true), + byte0(bytes[0]), byte1(bytes[1]) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + // Notice we don't compare bytes[0], as otherwise we'd be unnecessarily + // discarding MMXM. If that pattern is added this should be modified + return (bytes[3] == dict_bytes[3]) && (bytes[2] == dict_bytes[2]) && + (bytes[1] != dict_bytes[1]) && (match_location >= 0); + + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = {byte0, byte1, dict_bytes[2], dict_bytes[3]}; + return true; + } +}; + +class CPack::PatternZZZX : public Pattern +{ + private: + /** + * A copy of the unmatched byte. + */ + const uint8_t byte; + + public: + PatternZZZX(const std::array bytes, const int match_location) + : Pattern(ZZZX, 0xD, 4, 1, 0, false), byte(bytes[0]) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + return (bytes[3] == 0) && (bytes[2] == 0) && (bytes[1] == 0) && + (bytes[0] != 0); + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = {byte, 0, 0, 0}; + return false; + } +}; + +class CPack::PatternMMMX : public Pattern +{ + private: + /** + * A copy of the unmatched byte. + */ + const uint8_t byte; + + public: + PatternMMMX(const std::array bytes, const int match_location) + : Pattern(MMMX, 0xE, 8, 1, match_location, true), + byte(bytes[0]) {} + + static bool isPattern(const std::array& bytes, + const std::array& dict_bytes, + const int match_location) + { + return (bytes[3] == dict_bytes[3]) && (bytes[2] == dict_bytes[2]) && + (bytes[1] == dict_bytes[1]) && (bytes[0] != dict_bytes[0]) && + (match_location >= 0); + } + + bool decompress(const std::array dict_bytes, + std::array& data) const override + { + data = {byte, dict_bytes[1], dict_bytes[2], dict_bytes[3]}; + return true; + } +}; + +class CPack::CompData : public CompressionData +{ + public: + /** + * The patterns matched in the original line. + */ + std::vector> entries; + + /** + * Default constructor. + * + * @param dictionary_size Number of entries in the dictionary. + */ + CompData(const std::size_t dictionary_size); + + /** + * Default destructor. + */ + ~CompData(); +}; + +#endif //__MEM_CACHE_COMPRESSORS_CPACK_HH__