mem-ruby: Parameterize xor bits in BlockBloomFilter
Parameterize bitfield ranges in BlockBloomFilter such that the
hash is applied between masked bitfields of an address.
Change-Id: I008bd873458e9815e98530e308491adb65bb34cb
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18870
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
diff --git a/src/mem/ruby/filters/BlockBloomFilter.cc b/src/mem/ruby/filters/BlockBloomFilter.cc
index 0718c96..f5f7a91 100644
--- a/src/mem/ruby/filters/BlockBloomFilter.cc
+++ b/src/mem/ruby/filters/BlockBloomFilter.cc
@@ -29,11 +29,26 @@
#include "mem/ruby/filters/BlockBloomFilter.hh"
#include "base/bitfield.hh"
+#include "base/logging.hh"
#include "params/BlockBloomFilter.hh"
BlockBloomFilter::BlockBloomFilter(const BlockBloomFilterParams* p)
- : AbstractBloomFilter(p)
+ : AbstractBloomFilter(p), masksLSBs(p->masks_lsbs),
+ masksSizes(p->masks_sizes)
{
+ fatal_if(masksLSBs.size() != masksSizes.size(),
+ "Masks haven't been properly provided");
+ fatal_if(masksLSBs.size() < 2,
+ "There must be at least two masks to XOR");
+
+ for (int i = 0; i < masksLSBs.size(); i++) {
+ fatal_if((masksSizes[i] > sizeBits) || (masksSizes[i] <= 0),
+ "The bitfields must be indexable in the filter");
+ fatal_if(masksLSBs[i] + masksSizes[i] >
+ std::numeric_limits<Addr>::digits,
+ "The total size of the bitfields cannot be bigger than the " \
+ "number of bits in an address");
+ }
}
BlockBloomFilter::~BlockBloomFilter()
@@ -61,16 +76,14 @@
int
BlockBloomFilter::hash(Addr addr) const
{
- // Pull out some bit field ==> B1
- // Pull out additional bits, not the same as B1 ==> B2
- // XOR B1 and B2 to get hash index
- Addr block_bits = bits(addr, 2 * offsetBits - 1, offsetBits);
- int offset = 5;
- Addr other_bits = bits(addr, 2 * offsetBits + offset + sizeBits - 1,
- 2 * offsetBits + offset);
- int index = block_bits ^ other_bits;
- assert(index < filter.size());
- return index;
+ Addr hashed_addr = 0;
+ for (int i = 0; i < masksLSBs.size(); i++) {
+ hashed_addr ^=
+ bits(addr, offsetBits + masksLSBs[i] + masksSizes[i] - 1,
+ offsetBits + masksLSBs[i]);
+ }
+ assert(hashed_addr < filter.size());
+ return hashed_addr;
}
BlockBloomFilter*
diff --git a/src/mem/ruby/filters/BlockBloomFilter.hh b/src/mem/ruby/filters/BlockBloomFilter.hh
index c386624..280793c 100644
--- a/src/mem/ruby/filters/BlockBloomFilter.hh
+++ b/src/mem/ruby/filters/BlockBloomFilter.hh
@@ -29,10 +29,16 @@
#ifndef __MEM_RUBY_FILTERS_BLOCKBLOOMFILTER_HH__
#define __MEM_RUBY_FILTERS_BLOCKBLOOMFILTER_HH__
+#include <vector>
+
#include "mem/ruby/filters/AbstractBloomFilter.hh"
struct BlockBloomFilterParams;
+/**
+ * Simple deletable (with false negatives) bloom filter that extracts
+ * bitfields of an address to use as indexes of the filter vector.
+ */
class BlockBloomFilter : public AbstractBloomFilter
{
public:
@@ -44,7 +50,19 @@
int getCount(Addr addr) const override;
private:
+ /**
+ * XOR hash between bitfields of an address, provided by the mask vector.
+ *
+ * @param addr The address to be hashed.
+ * @return The value of the XOR of the masked bitfields of the address.
+ */
int hash(Addr addr) const;
+
+ /** Position of the LSB of each mask. */
+ std::vector<unsigned> masksLSBs;
+
+ /** Number of bits in each mask. */
+ std::vector<unsigned> masksSizes;
};
#endif // __MEM_RUBY_FILTERS_BLOCKBLOOMFILTER_HH__
diff --git a/src/mem/ruby/filters/BloomFilters.py b/src/mem/ruby/filters/BloomFilters.py
index 93d4dec..89a4b9b 100644
--- a/src/mem/ruby/filters/BloomFilters.py
+++ b/src/mem/ruby/filters/BloomFilters.py
@@ -48,6 +48,11 @@
cxx_class = 'BlockBloomFilter'
cxx_header = "mem/ruby/filters/BlockBloomFilter.hh"
+ masks_lsbs = VectorParam.Unsigned([Self.offset_bits,
+ 2 * Self.offset_bits], "Position of the LSB of each mask")
+ masks_sizes = VectorParam.Unsigned([Self.offset_bits, Self.offset_bits],
+ "Size, in number of bits, of each mask")
+
class BulkBloomFilter(AbstractBloomFilter):
type = 'BulkBloomFilter'
cxx_class = 'BulkBloomFilter'
