derek/gem5
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mem-ruby: Parameterize xor bits in BlockBloomFilter

Browse Source 
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>
This commit is contained in:
Daniel R. Carvalho
2019-05-09 22:12:59 +02:00
committed by Daniel Carvalho
parent 7584c390eb
commit e3f9e2097f
3 changed files with 47 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
src/mem/ruby/filters/BlockBloomFilter.cc
View File

@@ -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 @@ BlockBloomFilter::getCount(Addr addr) const
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*

18
src/mem/ruby/filters/BlockBloomFilter.hh
View File

@@ -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 @@ class BlockBloomFilter : public AbstractBloomFilter
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__

5
src/mem/ruby/filters/BloomFilters.py
View File

@@ -48,6 +48,11 @@ class BlockBloomFilter(AbstractBloomFilter):
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'