166 lines
5.2 KiB
Python
166 lines
5.2 KiB
Python
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"""OID tree traversal for the garbage collection phase of packing.
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Optimized for memory efficiency. Uses sets of native integers
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rather than Python integers because native integers take up a lot less
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room in RAM.
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"""
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from __future__ import absolute_import
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import BTrees
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import collections
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import gc
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import logging
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from relstorage._compat import iteritems
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IIunion32 = BTrees.family32.II.union
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IISet32 = BTrees.family32.II.Set
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IISet64 = BTrees.family64.II.Set
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log = logging.getLogger(__name__)
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class IISet32X(object):
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"""An IISet32 extended with a Python set layer for efficient inserts."""
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def __init__(self):
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self._base = IISet32()
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self._layer = set()
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def add(self, key):
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layer = self._layer
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if key not in layer and key not in self._base:
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layer.add(key)
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if len(layer) > 10000:
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self._apply()
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def _apply(self):
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"""Add the layer to the base and reset the layer."""
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if self._layer:
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self._base = IIunion32(self._base, IISet32(self._layer))
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self._layer.clear()
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def __iter__(self):
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self._apply()
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return iter(self._base)
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def __contains__(self, key):
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return key in self._layer or key in self._base
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class TreeMarker(object):
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"""Finds all OIDs reachable from a set of root OIDs."""
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# This class groups OIDs by their upper 33 bits. Why 33 instead
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# of 32? Because IISet and IIBucket are signed, they can not accept
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# positive integers >= (1 << 31). The solution is to simply
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# add an extra grouping bit.
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hi = 0xffffffff80000000 # 33 high bits
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lo = 0x000000007fffffff # 31 low bits
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def __init__(self):
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# self._refs:
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# {from_oid_hi: {to_oid_hi: IISet64([from_oid_lo << 32 | to_oid_lo])}}
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self._refs = collections.defaultdict(
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lambda: collections.defaultdict(IISet64))
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# self._reachable: {oid_hi: IISet32X}
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self._reachable = collections.defaultdict(IISet32X)
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self.reachable_count = 0
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def add_refs(self, pairs):
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"""Add a list of (from_oid, to_oid) reference pairs.
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`from_oid` and `to_oid` must be 64 bit integers.
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"""
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refs = self._refs
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hi = self.hi
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lo = self.lo
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for from_oid, to_oid in pairs:
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s = refs[from_oid & hi][to_oid & hi]
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s.add(((from_oid & lo) << 32) | (to_oid & lo))
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def mark(self, oids):
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"""Mark specific OIDs and descendants of those OIDs as reachable."""
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hi = self.hi
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lo = self.lo
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pass_count = 1
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# this_pass: {oid_hi: IISet32X}
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this_pass = collections.defaultdict(IISet32X)
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for oid in sorted(oids):
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this_pass[oid & hi].add(int(oid & lo))
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while this_pass:
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gc.collect()
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found, next_pass = self._mark_pass(this_pass)
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log.debug(
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"Found %d more referenced object(s) in pass %d",
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found, pass_count)
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if not found:
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break
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self.reachable_count += found
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pass_count += 1
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this_pass = next_pass
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return pass_count
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def _mark_pass(self, this_pass):
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"""Mark OIDs as reachable. Produce an OID set for the next pass.
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Return (found, next_pass), where `found` is the number of
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new OIDs marked and `next_pass` is the collection of OIDs to
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follow in the next pass.
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"""
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# pylint:disable=too-many-locals
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# next_pass: {oid_hi: IISet32X}
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next_pass = collections.defaultdict(IISet32X)
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found = 0
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refs = self._refs
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reachable = self._reachable
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lo = self.lo
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for oid_hi, oids_lo in iteritems(this_pass):
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from_reachable_set = reachable[oid_hi]
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for oid_lo in oids_lo:
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if oid_lo in from_reachable_set:
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# This OID is already known to be reachable.
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continue
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found += 1
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from_reachable_set.add(oid_lo)
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if oid_hi not in refs:
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# This OID doesn't reference anything.
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continue
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# Add the children of this OID to next_pass.
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for to_oid_hi, s in iteritems(refs[oid_hi]):
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min_key = oid_lo << 32
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max_key = min_key | 0xffffffff
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keys = s.keys(min=min_key, max=max_key)
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if not keys:
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# No references found here.
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continue
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to_reachable_set = reachable[to_oid_hi]
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next_pass_add = next_pass[to_oid_hi].add
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for key in keys:
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child_oid_lo = int(key & lo)
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if child_oid_lo not in to_reachable_set:
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next_pass_add(child_oid_lo)
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return found, next_pass
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def free_refs(self):
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"""Free the collection of refs to save RAM."""
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self._refs = None
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gc.collect()
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@property
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def reachable(self):
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"""Iterate over all the reachable OIDs."""
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for oid_hi, oids_lo in iteritems(self._reachable):
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for oid_lo in oids_lo:
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# Decode the OID.
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yield oid_hi | oid_lo
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