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Commit 9c47277a authored by Tim Peters's avatar Tim Peters
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Massive rewrite to make simul.py's circular cache aware of 

MVCC.  It isn't blowing up, but it thinks the hit rate is
100% -- might have missed something there <wink>.
parent 15bb2e12
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Showing with 274 additions and 145 deletions
src/ZEO/cache.py
View file @ 9c47277a
......@@ -205,17 +205,20 @@ class ClientCache(object):
if L is None:
self._trace(0x24, oid, tid)
return None
# A pair with None as the second element will always be less
# than any pair with the same first tid.
# A pair with None as the second element is less than any pair with
# the same first tid. Dubious: this relies on that None is less
# than any comparable non-None object in recent Pythons.
i = bisect.bisect_left(L, (tid, None))
# The least element left of tid was written before tid. If
# there is no element, the cache doesn't have old enough data.
# Now L[i-1] < (tid, None) < L[i], and the start_tid for everything in
# L[:i} is < tid, and the start_tid for everything in L[i:] is >= tid.
# Therefore the largest start_tid < tid must be at L[i-1]. If i is 0,
# there is no start_tid < tid: we don't have any data old enougn.
if i == 0:
self._trace(0x24, oid, tid)
return
lo, hi = L[i-1]
# lo should always be less than tid
if not lo < tid <= hi:
assert lo < tid
if tid > hi: # we don't have any data in the right range
self._trace(0x24, oid, tid)
return None
o = self.fc.access((oid, lo))
......@@ -284,7 +287,7 @@ class ClientCache(object):
p = start_tid, end_tid
if p in L:
return # duplicate store
bisect.insort_left(L, (start_tid, end_tid))
bisect.insort_left(L, p)
self._trace(0x54, oid, version, start_tid, end_tid,
dlen=len(data))
self.fc.add(o)
......@@ -457,7 +460,7 @@ class ClientCache(object):
self._trace = notrace
def _trace(self,
code, oid="", version="", tid="", end_tid=z64, dlen=0,
code, oid="", version="", tid=z64, end_tid=z64, dlen=0,
# The next two are just speed hacks.
time_time=time.time, struct_pack=struct.pack):
# The code argument is two hex digits; bits 0 and 7 must be zero.
......
src/ZEO/simul.py
View file @ 9c47277a
......@@ -34,12 +34,14 @@ import time
import getopt
import struct
import math
import bisect
from sets import Set
from ZODB.utils import z64
def usage(msg):
print >>sys.stderr, msg
print >>sys.stderr, __doc__
print >> sys.stderr, msg
print >> sys.stderr, __doc__
def main():
# Parse options.
......@@ -143,7 +145,7 @@ def main():
code & 0x7e,
code & 0x01)
# And pass it to the simulation.
sim.event(ts, dlen, version, code, current, oid, start_tid)
sim.event(ts, dlen, version, code, current, oid, start_tid, end_tid)
f.close()
# Finish simulation.
......@@ -185,7 +187,8 @@ class Simulation(object):
self.writes = 0
self.ts0 = None
def event(self, ts, dlen, _version, code, _current, oid, _serial):
def event(self, ts, dlen, _version, code, _current, oid,
start_tid, end_tid):
# Record first and last timestamp seen.
if self.ts0 is None:
self.ts0 = ts
......@@ -203,15 +206,14 @@ class Simulation(object):
self.loads += 1
self.total_loads += 1
assert (dlen == 0) == (code in (0x20, 0x24))
if dlen:
self.load(oid, dlen)
self.load(oid, dlen, start_tid)
elif action == 0x50:
# Store.
assert dlen
self.write(oid, dlen)
self.write(oid, dlen, start_tid, end_tid)
elif action == 0x10:
# Invalidate.
self.inval(oid)
self.inval(oid, start_tid)
elif action == 0x00:
# Restart.
self.report()
......@@ -219,14 +221,14 @@ class Simulation(object):
else:
raise ValueError("unknown trace code 0x%x" % code)
def write(self, oid, size):
def write(self, oid, size, start_tid, end_tid):
pass
def load(self, oid, size):
def load(self, oid, size, start_tid):
# Must increment .hits and .total_hits as appropriate.
pass
def inval(self, oid):
def inval(self, oid, start_tid):
# Must increment .invals and .total_invals as appropriate.
pass
......@@ -280,6 +282,255 @@ class Simulation(object):
for name in self.extras])
print (self.format + " OVERALL") % args
from ZEO.cache import ZEC3_HEADER_SIZE
# An Entry just wraps a (key, offset) pair. A key is in turn an
# (oid, tid) pair.
from ZEO.cache import Entry
class CircularCacheSimulation(Simulation):
# The cache is managed as a single file with a pointer that
# goes around the file, circularly, forever. New objects
# are written at the current pointer, evicting whatever was
# there previously.
extras = "evicts", "inuse"
def __init__(self, cachelimit):
from ZEO import cache
from BTrees.OIBTree import OIBTree
Simulation.__init__(self, cachelimit)
self.total_evicts = 0
# Current offset in file.
self.offset = ZEC3_HEADER_SIZE
# Map offset in file to (size, Entry) pair, or to (size, None) if
# the offset starts a free block.
self.filemap = {ZEC3_HEADER_SIZE: (self.cachelimit - ZEC3_HEADER_SIZE,
None)}
# Map key to Entry. A key is an (oid, tid) pair.
self.key2entry = {}
# Map oid to tid of current revision.
self.current = {}
# Map oid to list of (start_tid, end_tid) pairs in sorted order.
# Used to find matching key for load of non-current data.
self.noncurrent = {}
# Map key (an (oid, tid) pair) to the size of the object state.
# Unlike the others, this accumulates knowledge over time, regardless
# of what's in the cache. The problem: the trace file may have
# a load hit where we have a load miss. There won't be a store in
# the trace file "soon" since the actual cache had the data. What
# can the simulated cache do? If the object has ever been seen
# before, it can look up its size in this dict, and "pretend" to
# do a store. This isn't faithful in all cases, since we don't
# know the right tid: if we miss on a plain load(), the trace
# fail contains no indication of the appropriate tid.
self.key2size = OIBTree()
# The number of overhead bytes needed to store an object pickle
# on disk (all bytes beyond those needed for the object pickle).
self.overhead = (cache.Object.TOTAL_FIXED_SIZE +
cache.OBJECT_HEADER_SIZE)
def restart(self):
Simulation.restart(self)
self.evicts = 0
def load(self, oid, size, tid):
if tid == z64:
# Trying to load current revision.
if oid in self.current:
self.hits += 1
self.total_hits += 1
else:
self._cache_miss(oid, tid)
return
# May or may not be trying to load current revisiion.
cur_tid = self.current.get(oid)
if cur_tid == tid:
self.hits += 1
self.total_hits += 1
return
# It's a load for non-current data. Do we know about this oid?
L = self.noncurrent.get(oid)
if L is None:
self._cache_miss(oid, tid)
return
i = bisect.bisect_left(L, (tid, None))
if i == 0:
# This tid is smaller than any we know about -- miss.
self._cache_miss(oid, tid)
return
lo, hi = L[i-1]
assert lo < tid
if tid > hi:
self._cache_miss(oid, tid)
return
# Cache hit.
self.hits += 1
self.total_hits += 1
def _cache_miss(self, oid, tid, HUGE64='\xff'*8):
have_data = False
if tid == z64:
# Miss on current data. Find the most revision we ever saw.
items = self.key2size.items(min=(oid, z64), max=(oid, HUGE64))
if items:
(oid, tid), size = items[-1] # most recent
have_data = True
else:
# Miss on non-current data. Find one "that fits", approximately.
items = self.key2size.items(min=(oid, tid), max=(oid, HUGE64))
if items:
(oid, tid), size = items[0] # first one at or after tid
have_data = True
if have_data:
# Pretend the cache miss was followed by a store.
self.writes += 1
self.total_writes += 1
self.add(oid, tid, size)
# (oid, tid) is in the cache. Remove it: take it out of key2entry,
# and in `filemap` mark the space it occupied as being free.
def _remove(self, oid, tid):
key = oid, tid
e = self.key2entry.pop(key)
pos = e.offset
size, _e = self.filemap[pos]
assert e is _e
self.filemap[pos] = size, None
def _remove_noncurrent_revisions(self, oid):
noncurrent_list = self.noncurrent.get(oid)
if noncurrent_list:
self.invals += len(noncurrent_list)
self.total_invals += len(noncurrent_list)
for start_tid, end_tid in noncurrent_list:
self._remove(oid, start_tid)
del self.noncurrent[oid]
def inval(self, oid, tid):
if tid == z64:
# This is part of startup cache verification.
self._remove_noncurrent_revisions(oid, version)
cur_tid = self.current.get(oid)
if cur_tid is None:
# We don't have current data, so nothing to do.
return
# We had current data for oid, but no longer.
self.invals += 1
self.total_invals += 1
del self.current[oid]
if tid == z64:
# Startup cache verification: forget this oid entirely.
self._remove(oid, current_tid)
return
# Add the validty range to the list of non-current data for oid.
assert cur_tid < tid
L = self.noncurrent.setdefault(oid, [])
bisect.insort_left(L, (cur_tid, tid))
def write(self, oid, size, start_tid, end_tid):
if end_tid == z64:
# Storing current revision.
if oid in self.current: # we already have it in cache
return
self.current[oid] = start_tid
self.key2size[oid, start_tid] = size
self.writes += 1
self.total_writes += 1
self.add(oid, start_tid, size)
return
# Storing non-current revision.
L = self.noncurrent.setdefault(oid, [])
p = start_tid, end_tid
if p in L:
return # we already have it in cache
bisect.insort_left(L, p)
self.key2size[(oid, start_tid)] = size
self.writes += 1
self.total_writes += 1
self.add(oid, start_tid, size)
def add(self, oid, tid, size):
size += self.overhead
avail = self.makeroom(size)
key = oid, tid
assert key not in self.key2entry
e = Entry(key, self.offset)
self.filemap[self.offset] = size, e
self.key2entry[key] = e
self.offset += size
# All the space made available must be accounted for in filemap.
excess = avail - size
if excess:
self.filemap[self.offset] = excess, None
def makeroom(self, need):
# Evict enough objects to make the necessary space available.
if self.offset + need > self.cachelimit:
self.offset = ZEC3_HEADER_SIZE
pos = self.offset
while need > 0:
assert pos < self.cachelimit
try:
size, e = self.filemap[pos]
except KeyError:
self.dump()
raise
del self.filemap[pos]
if e:
self.evicts += 1
self.total_evicts += 1
assert pos == e.offset
_e = self.key2entry.pop(e.key)
assert e is _e
need -= size
pos += size
return pos - self.offset # total number of bytes freed
def report(self):
self.check()
free = used = total = 0
for size, e in self.filemap.itervalues():
total += size
if e:
used += size
else:
free += size
self.inuse = round(100.0 * used / total, 1)
self.total_inuse = self.inuse
Simulation.report(self)
def check(self):
oidcount = 0
pos = ZEC3_HEADER_SIZE
while pos < self.cachelimit:
size, e = self.filemap[pos]
if e:
oidcount += 1
assert self.key2entry[e.key].offset == pos
pos += size
assert oidcount == len(self.key2entry)
assert pos == self.cachelimit
def dump(self):
print len(self.filemap)
L = list(self.filemap)
L.sort()
for k in L:
v = self.filemap[k]
print k, v[0], repr(v[1])
class ZEOCacheSimulation(Simulation):
"""Simulate the ZEO 1.0 and 2.0cache behavior.
......@@ -971,131 +1222,6 @@ class OracleSimulation(LRUCacheSimulation):
print "Scanned file, %d unique oids, %d repeats" % (
all, len(self.count))
from ZEO.cache import ZEC3_HEADER_SIZE
class CircularCacheSimulation(Simulation):
# The cache is managed as a single file with a pointer that
# goes around the file, circularly, forever. New objects
# are written at the current pointer, evicting whatever was
# there previously.
extras = "evicts", "inuse"
def __init__(self, cachelimit):
from ZEO import cache
Simulation.__init__(self, cachelimit)
self.total_evicts = 0
# Current offset in file.
self.offset = ZEC3_HEADER_SIZE
# Map offset in file to (size, oid) pair.
self.filemap = {ZEC3_HEADER_SIZE: (self.cachelimit - ZEC3_HEADER_SIZE,
None)}
# Map oid to file offset.
self.oid2ofs = {}
self.overhead = (cache.Object.TOTAL_FIXED_SIZE +
cache.OBJECT_HEADER_SIZE)
def restart(self):
Simulation.restart(self)
self.evicts = 0
def load(self, oid, size):
if oid in self.oid2ofs:
self.hits += 1
self.total_hits += 1
elif size:
self.writes += 1
self.total_writes += 1
self.add(oid, size)
# Else it was a load miss in the trace file, and a load miss here too.
def inval(self, oid):
pos = self.oid2ofs.pop(oid, None)
if pos is None:
return
self.invals += 1
self.total_invals += 1
size, _oid = self.filemap[pos]
assert oid == _oid
self.filemap[pos] = size, None
def write(self, oid, size):
if oid not in self.oid2ofs:
self.writes += 1
self.total_writes += 1
self.add(oid, size)
def add(self, oid, size):
size += self.overhead
avail = self.makeroom(size)
assert oid not in self.oid2ofs
self.filemap[self.offset] = size, oid
self.oid2ofs[oid] = self.offset
self.offset += size
# All the space made available must be accounted for in filemap.
excess = avail - size
if excess:
self.filemap[self.offset] = excess, None
def makeroom(self, need):
# Evict enough objects to make the necessary space available.
if self.offset + need > self.cachelimit:
self.offset = ZEC3_HEADER_SIZE
pos = self.offset
while need > 0:
assert pos < self.cachelimit
try:
size, oid = self.filemap[pos]
except KeyError:
self.dump()
raise
del self.filemap[pos]
if oid:
self.evicts += 1
self.total_evicts += 1
_pos = self.oid2ofs.pop(oid)
assert pos == _pos
need -= size
pos += size
return pos - self.offset # total number of bytes freed
def report(self):
self.check()
free = used = total = 0
for size, oid in self.filemap.itervalues():
total += size
if oid:
used += size
else:
free += size
self.inuse = round(100.0 * used / total, 1)
self.total_inuse = self.inuse
Simulation.report(self)
def check(self):
oidcount = 0
pos = ZEC3_HEADER_SIZE
while pos < self.cachelimit:
size, oid = self.filemap[pos]
if oid:
oidcount += 1
assert self.oid2ofs[oid] == pos
pos += size
assert oidcount == len(self.oid2ofs)
assert pos == self.cachelimit
def dump(self):
print len(self.filemap)
L = list(self.filemap)
L.sort()
for k in L:
v = self.filemap[k]
print k, v[0], repr(v[1])
class BuddyCacheSimulation(LRUCacheSimulation):
def __init__(self, cachelimit):
......
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