Set default pagesize to 8k

Also reduce read ahead / delayed write parameters
so we don't need too much memory in merge procs.

README.md

@@ -38,7 +38,7 @@ Put these values in your `app.config` in the `hanoi` section
           {data_root, "./data/hanoi"},
           {compress, none | snappy | gzip},
           {sync_strategy, none | sync | {seconds, N}},
-          {page_size, 32768}
+          {page_size, 8192}
          ]},
 ```
 

src/hanoi_reader.erl

@@ -46,7 +46,7 @@ open(Name) ->
 
 %% this is how to open a btree for sequential scanning (merge, fold)
 open(Name, sequential) ->
-    {ok, File} = file:open(Name, [raw,read,{read_ahead, 1024 * 512},binary]),
+    {ok, File} = file:open(Name, [raw,read,{read_ahead, 1024 * 32},binary]),
     open2(Name, File);
 
 %% this is how to open a btree for random access

src/hanoi_writer.erl

@@ -31,7 +31,7 @@
 %% Streaming btree writer. Accepts only monotonically increasing keys for put.
 %%
 
--define(NODE_SIZE, 32*1024).
+-define(NODE_SIZE, 8*1024).
 
 -behavior(gen_server).
 
@@ -82,15 +82,15 @@ init([Name,Options]) ->
     Size = proplists:get_value(size, Options, 2048),
 
 %    io:format("got name: ~p~n", [Name]),
-
+    BlockSize = hanoi:get_opt(block_size, Options, ?NODE_SIZE),
     case file:open( hanoi_util:index_file_name(Name),
-                               [raw, exclusive, write, {delayed_write, 512 * 1024, 2000}]) of
+                               [raw, exclusive, write, {delayed_write, BlockSize * 4, 2000}]) of
         {ok, IdxFile} ->
             {ok, BloomFilter} = ebloom:new(erlang:min(Size,16#ffffffff), 0.01, 123),
             {ok, #state{ name=Name,
                          index_file_pos=0, index_file=IdxFile,
                          bloom = BloomFilter,
-                         block_size = hanoi:get_opt(block_size, Options, ?NODE_SIZE),
+                         block_size = BlockSize,
                          compress = hanoi:get_opt(compress, Options, none)
                        }};
         {error, _}=Error ->