Commit 5664b307 authored by Tim Peters's avatar Tim Peters

Removed the `key2size` OIBTree.

Maintaining this is a significant expense; the code didn't
make real use of it; and every time I've tried to exploit it
I've ended up with grossly too-large simulated hit rates.
Would probably take another day to figure out exactly why that
is, and the simulated rates are "good enough" now without it.
parent 8a4983e8
......@@ -196,7 +196,8 @@ class Simulation(object):
# Load.
self.loads += 1
self.total_loads += 1
assert (dlen == 0) == (code in (0x20, 0x24))
# Asserting that dlen is 0 iff it's a load miss.
# assert (dlen == 0) == (code in (0x20, 0x24))
self.load(oid, dlen, start_tid)
elif action == 0x50:
# Store.
......@@ -310,7 +311,6 @@ class CircularCacheSimulation(Simulation):
def __init__(self, cachelimit):
from ZEO import cache
from BTrees.OIBTree import OIBTree
Simulation.__init__(self, cachelimit)
self.total_evicts = 0 # number of cache evictions
......@@ -332,18 +332,6 @@ class CircularCacheSimulation(Simulation):
# 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 +
......@@ -356,11 +344,9 @@ class CircularCacheSimulation(Simulation):
def load(self, oid, size, tid):
if tid == z64:
# Trying to load current revision.
if oid in self.current:
if oid in self.current: # else it's a cache miss
self.hits += 1
self.total_hits += 1
else:
self._cache_miss(oid, tid)
return
# May or may not be trying to load current revision.
......@@ -373,44 +359,20 @@ class CircularCacheSimulation(Simulation):
# 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
return # cache miss
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)
# No data in the right tid range -- miss.
return
# Cache hit.
self.hits += 1
self.total_hits += 1
def _cache_miss(self, oid, tid, HUGE64='\xff'*8):
return
have_data = False
if tid == z64:
# Miss on current data. Find the most recent 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, size, tid)
# (oid, tid) is in the cache. Remove it: take it out of key2entry,
# and in `filemap` mark the space it occupied as being free. The
# caller is responsible for removing it from `current` or `noncurrent`.
......@@ -467,7 +429,6 @@ class CircularCacheSimulation(Simulation):
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, size, start_tid)
......@@ -478,7 +439,6 @@ class CircularCacheSimulation(Simulation):
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, size, start_tid, end_tid)
......
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