b7223e0976
Implement a perfect compressor that always manages to compresses data exactly to its maximum allowed compression ratio. This allows tracking a compression upper bound. Change-Id: Ibc68bf2dc84b75207795d5ba6304b9ed6dbeae8f Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21160 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
89 lines
3.1 KiB
C++
89 lines
3.1 KiB
C++
/*
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* Copyright (c) 2019 Inria
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Daniel Carvalho
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*/
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/** @file
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* Implementation of a perfect compressor, which compresses data to its
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* maximum allowed compression ratio.
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*/
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#include "mem/cache/compressors/perfect.hh"
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#include <algorithm>
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#include "debug/CacheComp.hh"
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#include "params/PerfectCompressor.hh"
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PerfectCompressor::CompData::CompData(const uint64_t* data,
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std::size_t num_entries)
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: CompressionData(), entries(data, data + num_entries)
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{
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}
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PerfectCompressor::PerfectCompressor(const Params *p)
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: BaseCacheCompressor(p),
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compressedSize(8 * blkSize / p->max_compression_ratio),
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compressionLatency(p->compression_latency),
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decompressionLatency(p->decompression_latency)
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{
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}
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std::unique_ptr<BaseCacheCompressor::CompressionData>
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PerfectCompressor::compress(const uint64_t* cache_line, Cycles& comp_lat,
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Cycles& decomp_lat)
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{
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// Compress every word sequentially
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std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data(
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new CompData(cache_line, blkSize/8));
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// Set relevant metadata
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comp_data->setSizeBits(compressedSize);
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comp_lat = compressionLatency;
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decomp_lat = decompressionLatency;
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return comp_data;
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}
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void
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PerfectCompressor::decompress(const CompressionData* comp_data,
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uint64_t* data)
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{
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// Decompress every entry sequentially
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const std::vector<uint64_t>& entries =
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static_cast<const CompData*>(comp_data)->entries;
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assert(entries.size() == (blkSize/8));
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std::copy(entries.begin(), entries.end(), data);
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}
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PerfectCompressor*
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PerfectCompressorParams::create()
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{
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return new PerfectCompressor(this);
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}
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