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records (requiring occasional seeks).

hits found in the non-current file into the current file.

For the 40-hour trace starting on Sept 4 at 6pm, this increases the
hit rate from 83.2% to 87.0% (IOW a decrease in miss rate from 16.8%
to 13%):

ZEOCacheSimulation, cache size 200,000,000 bytes
  START TIME  DURATION    LOADS     HITS INVALS WRITES  FLIPS HITRATE
Sep  4 18:00  40:36:34  1420070  1181176  16198  10014     15  83.2%

AltZEOCacheSimulation, cache size 200,000,000 bytes
  START TIME  DURATION    LOADS     HITS INVALS WRITES  FLIPS HITRATE
Sep  4 18:00  40:36:34  1420070  1235770  15384  10014     25  87.0%

the BuddyCacheSimulation constructor to round up the cachelimit so
that it reports the actual value used.

keeping track of the beginning and end address of all free blocks, to
make merging of adjacent blocks a breeze.  The free list is no longer
kept sorted order.

Unfortunately, this still performs poorly.  It has a higher hit rate
(with the 38 minute trace I'm using; the longer traces take too long)
than the buddy system allocator with the same arena size, it is *much*
slower, the memory usage is under 20% (!!!), and despite a roving
pointer, the allocation loop is taken an average of 692 times per
allocation.  At the end of the simulation the free list contains 1039
blocks; I presume this is a steady state approximating the average
behavior.  (There are 2280 allocated blocks at that point, roughly
confirming Knuth's "50% rule" and suggesting that the block merge code
works properly.)

I guess the next idea is separate free lists per size.

simple free list using a mix of exact-fit and last-fit with a roving
pointer as suggested by Tim.  Use -f to use this version.

Renamed BuddyNode to BlockNode since it is now used by both allocators.

Moved some code around in an attempt to organize it more top-down.

Moved the report printing into the Simulation base class.  Print the
class name and exact cache size before the header; skip the final
report printing if only one previous report was printed.

1000*1000.  This makes it easier to specify cache sizes for the buddy
system that don't have to be rounded up to the next power of two.  It
does make future reported results incompatible with past results.

allocator.

  invalidations instead of only the ones that hit the cache.

- Support reading gzipped files.  This is triggered automatically when
  the filename ends in .gz.  Also support reading from stdin (pass '-'
  as filename).

- Widen the FLIPS column by one to match the EVICTS column width of
  the LRU simulation.

- Support simulating alternative caching strategies.  For now, only
  LRU is supported, triggered by the -l option.

- Change the Simulation base class to store the cachelimit argument.
  (The constructor signature must be the same across all subclasses.)

base class.

report overall statistics for all columns.

ZEO_CACHE_TRACE set (see stats.py for file format description).