From fd2e0e870ca16f9b6d41acc4adac0c2a3e8beb16 Mon Sep 17 00:00:00 2001
From: Martin Sumner <martin.sumner@adaptip.co.uk>
Date: Mon, 25 Feb 2019 23:35:12 +0000
Subject: [PATCH] Align cache with default

Stop L0 from growing too large i.e. 127 * 4K is more than 10 times bigger than the default.
---
 priv/leveled.schema    |  2 +-
 src/leveled_bookie.erl | 22 +++++++---------------
 src/leveled_pmem.erl   |  6 ++++--
 3 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/priv/leveled.schema b/priv/leveled.schema
index 4498573..241ee33 100644
--- a/priv/leveled.schema
+++ b/priv/leveled.schema
@@ -21,7 +21,7 @@
 
 %% @doc The key size of the Bookie's in-memory cache 
 {mapping, "leveled.cache_size", "leveled.cache_size", [
-  {default, 4000},
+  {default, 2500},
   {datatype, integer},
   hidden
 ]}.
diff --git a/src/leveled_bookie.erl b/src/leveled_bookie.erl
index d7e5d4a..5b57e19 100644
--- a/src/leveled_bookie.erl
+++ b/src/leveled_bookie.erl
@@ -2187,21 +2187,13 @@ maybepush_ledgercache(MaxCacheSize, Cache, Penciller) ->
 
 -spec maybe_withjitter(integer(), integer()) -> boolean().
 %% @doc
-%% Push down randomly, but the closer to the maximum size, the more likely a 
-%% push should be
-maybe_withjitter(CacheSize, MaxCacheSize) ->
-    if
-        CacheSize > MaxCacheSize ->
-            R = leveled_rand:uniform(7 * MaxCacheSize),
-            if
-                (CacheSize - MaxCacheSize) > R ->
-                    true;
-                true ->
-                    false
-            end;
-        true ->
-            false
-    end.
+%% Push down randomly, but the closer to 4 * the maximum size, the more likely
+%% a push should be
+maybe_withjitter(CacheSize, MaxCacheSize) when CacheSize > MaxCacheSize ->
+    R = leveled_rand:uniform(4 * MaxCacheSize),
+    (CacheSize - MaxCacheSize) > R;
+maybe_withjitter(_CacheSize, _MaxCacheSize) ->
+    false.
 
 
 -spec get_loadfun(book_state()) -> fun().
diff --git a/src/leveled_pmem.erl b/src/leveled_pmem.erl
index e2de638..17b9277 100644
--- a/src/leveled_pmem.erl
+++ b/src/leveled_pmem.erl
@@ -44,6 +44,8 @@
 
 -include_lib("eunit/include/eunit.hrl").
 
+-define(MAX_CACHE_LINES, 31). % Must be less than 128
+
 % -type index_array() :: array:array().
 -type index_array() :: any()|none. % To live with OTP16
 
@@ -55,9 +57,9 @@
 
 -spec cache_full(list()) -> boolean().
 %% @doc
-%% If there are already 127 entries in the cache then the cache is full
+%% If there are already 31 entries in the cache then the cache is full
 cache_full(L0Cache) ->
-    length(L0Cache) == 127.
+    length(L0Cache) == ?MAX_CACHE_LINES.
 
 -spec prepare_for_index(index_array(), leveled_codec:segment_hash()) 
                                                             -> index_array().