Make it possible to configure generation sizes.

Document some more info about the types of the workloads and how they
respond to generation sizes.

relstorage/cache/local_client.py

@@ -37,6 +37,8 @@ class LocalClient(object):
         b'.b': bz2.decompress
     }
 
+    _bucket_type = LocalClientBucket
+
     def __init__(self, options, prefix=None):
         self._lock = threading.Lock()
         self.options = options
@@ -87,7 +89,7 @@ def _bucket0(self):
 
     def flush_all(self):
         with self._lock:
-            self.__bucket = LocalClientBucket(self._bucket_limit)
+            self.__bucket = self._bucket_type(self._bucket_limit)
             options = self.options
             if options.cache_local_dir:
                 _Loader.load_local_cache(options, self.prefix, self._bucket0)

relstorage/cache/mapping.py

@@ -53,7 +53,7 @@ class SizedLRUMapping(object):
     # When did we last age?
     _aged_at = 0
 
-
+    _cache_type = Cache
 
     def __init__(self, limit):
         # We experimented with using OOBTree and LOBTree
@@ -67,7 +67,7 @@ def __init__(self, limit):
         # large BTrees, but since that's not the case, we abandoned the idea.
 
         # This holds all the ring entries, no matter which ring they are in.
-        cache = self._cache = Cache(limit)
+        cache = self._cache = self._cache_type(limit)
         self._dict = cache.data
 
 

relstorage/cache/micro_benchmark_results.rst

@@ -157,6 +157,18 @@ web07           76,118   20,484    53,283      22,835   8
 web12           95,607   13,756    66,925      28,682   8
 ==========  ========== ======== =========  ========== ====
 
+Note that Financial1 and Financial2 are OLTP traces of a journal file,
+and orm-busy and orm-night are traces of an ORM session cache with
+short transactions. Both of these are dominated by *recency* and are
+thus very easy for LRU caches; a frequency cache like the new code has
+more trouble with them at smaller sizes. They are included to
+demonstrate worst-case performance and are probably not representative
+of typical RelStorage cache workloads (a RelStorage workload will have
+some objects, such as catalog BTree objects, that are frequently
+accessed which shouldn't be ejected if a more rare query occurs).
+The hit rates of these workloads are strongly correlated to the size
+of the eden generation.
+
 Cache simulation
 ----------------
 

relstorage/cache/tests/test_cache.py

@@ -17,6 +17,23 @@
 from relstorage.tests.util import skipOnCI
 from functools import partial
 
+from relstorage.cache.cache_ring import Cache as _BaseCache
+class Cache(_BaseCache):
+    # Tweak the generation sizes to match what we developed the tests with
+    _gen_protected_pct = 0.8
+    _gen_eden_pct = 0.1
+
+from relstorage.cache.mapping import SizedLRUMapping as _BaseSizedLRUMapping
+
+class SizedLRUMapping(_BaseSizedLRUMapping):
+    _cache_type = Cache
+
+from relstorage.cache.local_client import LocalClient as _BaseLocalClient
+
+class LocalClient(_BaseLocalClient):
+    _bucket_type = SizedLRUMapping
+
+
 class StorageCacheTests(unittest.TestCase):
 
     def setUp(self):
@@ -386,7 +403,6 @@ def assertNotNone(self, o):
             raise AssertionError("Expected not None")
 
     def getClass(self):
-        from relstorage.cache.mapping import SizedLRUMapping
         return SizedLRUMapping
 
     def test_age_empty(self):
@@ -738,7 +754,6 @@ def test_load_from_multiple_files_hit_limit(self):
 class LocalClientTests(unittest.TestCase):
 
     def getClass(self):
-        from relstorage.cache.local_client import LocalClient
         return LocalClient
 
     def _makeOne(self, **kw):
@@ -1123,7 +1138,6 @@ def test_bool(self):
         self.assertFalse(lru)
 
     def test_free_reuse(self):
-        from relstorage.cache.cache_ring import Cache
         cache = Cache(20)
         lru = cache.protected
         self.assertEqual(lru.limit, 16)