Daniel Carvalho has uploaded this change for review. (
https://gem5-review.googlesource.com/11103
Change subject: mem-cache: Add compression stats
......................................................................
mem-cache: Add compression stats
Add compression statistics to the compressors. It tracks
the number of blocks that can fit into a certain power
of two size, and the number of decompressions.
For example, if a block is compressed to 100 bits, it will
belong to the 128-bits compression size. Although it could
also fit bigger sizes, they are not taken into account for
the stats (i.e., the 100-bit compression will fit only the
128-bits size, not 256 or higher).
We save stats for compressions that fail (i.e., compressed
size is bigger than original cache line size).
Change-Id: Idab71a40a660e33259908ccd880e42a880b5ee06
---
M src/mem/cache/compressors/base.cc
M src/mem/cache/compressors/base.hh
2 files changed, 60 insertions(+), 1 deletion(-)
diff --git a/src/mem/cache/compressors/base.cc
b/src/mem/cache/compressors/base.cc
index 0f60eca..0513119 100644
--- a/src/mem/cache/compressors/base.cc
+++ b/src/mem/cache/compressors/base.cc
@@ -82,7 +82,16 @@
BaseCacheCompressor::compress(const uint8_t* cache_line)
{
Cycles lat;
- return compress(cache_line, lat);
+ std::unique_ptr<CompressionData> compression_data =
compress(cache_line,
+ lat);
+
+ // Get compressed size in bits
+ std::size_t compressed_size = compression_data->getSize()*8;
+
+ // Update stats
+ compressionSize[std::ceil(std::log2(compressed_size))]++;
+
+ return compression_data;
}
Cycles
@@ -101,5 +110,35 @@
assert(comp_data->matchLine(cache_line));
#endif
+ // Update number of decompressions
+ decompressions++;
+
return lat;
}
+
+void
+BaseCacheCompressor::regStats()
+{
+ ClockedObject::regStats();
+
+ using namespace Stats;
+
+ decompressions
+ .name(name() + ".decompressions")
+ .desc("Number of decompressions")
+ ;
+
+ // We also store when compression is bigger than original line size
+ compressionSize
+ .init(std::log2(lineSize*8) + 2)
+ .name(name() + ".compression_size")
+ .desc("Number of blocks that were compressed to this power of" \
+ "two size.")
+ ;
+
+ for (unsigned i = 0; i <= std::log2(lineSize*8) + 1; ++i) {
+ compressionSize.subname(i, std::to_string(1 << i));
+ compressionSize.subdesc(i, "Number of blocks that compressed to
fit " \
+ "in " + std::to_string(1 << i) + "
bits");
+ }
+}
diff --git a/src/mem/cache/compressors/base.hh
b/src/mem/cache/compressors/base.hh
index fc36942..a3b0dd8 100644
--- a/src/mem/cache/compressors/base.hh
+++ b/src/mem/cache/compressors/base.hh
@@ -119,6 +119,21 @@
const std::size_t lineSize;
/**
+ * @defgroup CompressionStats Compression specific statistics.
+ * @{
+ */
+
+ /** Total number of decompressions. */
+ Stats::Scalar decompressions;
+
+ /** Number of blocks that were compressed to this power of two size. */
+ Stats::Vector compressionSize;
+
+ /**
+ * @}
+ */
+
+ /**
* Apply the compression process to the cache line.
* Returns the number of cycles used by the compressor, however it is
* usually covered by a good pipelined execution, and is currently
ignored.
@@ -171,6 +186,11 @@
* @return Decompression latency in number of cycles.
*/
Cycles decompress(const CompressionData* comp_data);
+
+ /**
+ * Register local statistics.
+ */
+ void regStats();
};
#endif //__MEM_CACHE_COMPRESSORS_BASE_HH__
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: Idab71a40a660e33259908ccd880e42a880b5ee06
Gerrit-Change-Number: 11103
Gerrit-PatchSet: 1
Gerrit-Owner: Daniel Carvalho <[email protected]>
Gerrit-MessageType: newchange
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