src/base/filters/BloomFilters.py

# Copyright (c) 2019 Inria
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from m5.params import *
from m5.proxy import *
from m5.SimObject import SimObject


class BloomFilterBase(SimObject):
    type = "BloomFilterBase"
    abstract = True
    cxx_header = "base/filters/base.hh"
    cxx_class = "gem5::bloom_filter::Base"

    size = Param.Int(4096, "Number of entries in the filter")

    # By default assume that bloom filters are used for 64-byte cache lines
    offset_bits = Param.Unsigned(6, "Number of bits in a cache line offset")

    # Most of the filters are booleans, and thus saturate on 1
    num_bits = Param.Int(1, "Number of bits in a filter entry")
    threshold = Param.Int(1, "Value at which an entry is considered as set")


class BloomFilterBlock(BloomFilterBase):
    type = "BloomFilterBlock"
    cxx_class = "gem5::bloom_filter::Block"
    cxx_header = "base/filters/block_bloom_filter.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 BloomFilterMultiBitSel(BloomFilterBase):
    type = "BloomFilterMultiBitSel"
    cxx_class = "gem5::bloom_filter::MultiBitSel"
    cxx_header = "base/filters/multi_bit_sel_bloom_filter.hh"

    num_hashes = Param.Int(4, "Number of hashes")
    threshold = Self.num_hashes
    skip_bits = Param.Int(2, "Offset from block number")
    is_parallel = Param.Bool(False, "Whether hashing is done in parallel")


class BloomFilterBulk(BloomFilterMultiBitSel):
    type = "BloomFilterBulk"
    cxx_class = "gem5::bloom_filter::Bulk"
    cxx_header = "base/filters/bulk_bloom_filter.hh"


class BloomFilterH3(BloomFilterMultiBitSel):
    type = "BloomFilterH3"
    cxx_class = "gem5::bloom_filter::H3"
    cxx_header = "base/filters/h3_bloom_filter.hh"


class BloomFilterMulti(BloomFilterBase):
    type = "BloomFilterMulti"
    cxx_class = "gem5::bloom_filter::Multi"
    cxx_header = "base/filters/multi_bloom_filter.hh"

    # The base filter should not be used, since this filter is the combination
    # of multiple sub-filters, so we use a dummy value
    size = 1

    # By default there are two sub-filters that hash sequential bitfields
    filters = VectorParam.BloomFilterBase(
        [
            BloomFilterBlock(size=4096, masks_lsbs=[6, 12]),
            BloomFilterBlock(size=1024, masks_lsbs=[18, 24]),
        ],
        "Sub-filters to be combined",
    )

    # By default match this with the number of sub-filters
    threshold = 2


class BloomFilterPerfect(BloomFilterBase):
    type = "BloomFilterPerfect"
    cxx_class = "gem5::bloom_filter::Perfect"
    cxx_header = "base/filters/perfect_bloom_filter.hh"

    # The base filter is not needed. Use a dummy value.
    size = 1

    # This filter does not use saturating counters - as long as the entry is
    # set, it is present; thus, it only needs one bit.
    num_bits = 1
    threshold = 1