New config: {read|write}_buffer_size

These two parameters (defaulting to 512k) control
the amount of erlang file buffer space to allocate
for delayed_write and read_ahead when merging.

This config parameter is *per merge task* of which 
there can be many for each open HanoiDB; and again
multiplied by number of active vnodes in Riak.

As such, this can config parameter is significant
for the memory usage of a Riak with Hanoi, but setting
it too low will kill the performance.

README.md

@@ -39,6 +39,8 @@ Put these values in your `app.config` in the `hanoi` section
           {compress, none | snappy | gzip},
           {sync_strategy, none | sync | {seconds, N}},
           {page_size, 8192}
+          {write_buffer_size, 524288}  % 512kB
+          {read_buffer_size, 524288}  % 512kB
          ]},
 ```
 

src/hanoi_level.erl

@@ -167,12 +167,12 @@ initialize2(State) ->
             file:delete(BFileName),
             ok = file:rename(MFileName, AFileName),
 
-            {ok, BTA} = hanoi_reader:open(AFileName, random),
+            {ok, BTA} = hanoi_reader:open(AFileName, [random|State#state.opts]),
 
             case file:read_file_info(CFileName) of
                 {ok, _} ->
                     file:rename(CFileName, BFileName),
-                    {ok, BTB} = hanoi_reader:open(BFileName, random),
+                    {ok, BTB} = hanoi_reader:open(BFileName, [random|State#state.opts]),
                     check_begin_merge_then_loop(init_state(State#state{ a= BTA, b=BTB }));
 
                 {error, enoent} ->
@@ -182,12 +182,12 @@ initialize2(State) ->
         {error, enoent} ->
             case file:read_file_info(BFileName) of
                 {ok, _} ->
-                    {ok, BTA} = hanoi_reader:open(AFileName, random),
+                    {ok, BTA} = hanoi_reader:open(AFileName, [random|State#state.opts]),
-                    {ok, BTB} = hanoi_reader:open(BFileName, random),
+                    {ok, BTB} = hanoi_reader:open(BFileName, [random|State#state.opts]),
 
                     case file:read_file_info(CFileName) of
                         {ok, _} ->
-                            {ok, BTC} = hanoi_reader:open(CFileName, random);
+                            {ok, BTC} = hanoi_reader:open(CFileName, [random|State#state.opts]);
                         {error, enoent} ->
                             BTC = undefined
                     end,
@@ -201,7 +201,7 @@ initialize2(State) ->
 
                     case file:read_file_info(AFileName) of
                         {ok, _} ->
-                            {ok, BTA} = hanoi_reader:open(AFileName, random),
+                            {ok, BTA} = hanoi_reader:open(AFileName, [random|State#state.opts]),
                             main_loop(init_state(State#state{ a=BTA }));
 
                         {error, enoent} ->
@@ -259,7 +259,7 @@ main_loop(State = #state{ next=Next }) ->
 
             plain_rpc:send_reply(From, ok),
 
-            case hanoi_reader:open(ToFileName, random) of
+            case hanoi_reader:open(ToFileName, [random|State#state.opts]) of
                 {ok, BT} ->
                     if SetPos == #state.b ->
                             check_begin_merge_then_loop(setelement(SetPos, State, BT));
@@ -471,7 +471,7 @@ main_loop(State = #state{ next=Next }) ->
             % then, rename M to A, and open it
             AFileName = filename("A",State2),
             ok = file:rename(MFileName, AFileName),
-            {ok, BT} = hanoi_reader:open(AFileName, random),
+            {ok, BT} = hanoi_reader:open(AFileName, [random|State#state.opts]),
 
             % iff there is a C file, then move it to B position
             % TODO: consider recovery for this
@@ -703,7 +703,7 @@ start_range_fold(FileName, WorkerPID, Range, State) ->
         proc_lib:spawn( fun() ->
                                 ?log("start_range_fold ~p on ~p -> ~p", [self, FileName, WorkerPID]),
                                 erlang:link(WorkerPID),
-                                {ok, File} = hanoi_reader:open(FileName, sequential),
+                                {ok, File} = hanoi_reader:open(FileName, [sequential|State#state.opts]),
                                 do_range_fold(File, WorkerPID, self(), Range),
                                 erlang:unlink(WorkerPID),
                                 hanoi_reader:close(File),

src/hanoi_merger.erl

@@ -41,8 +41,8 @@
 -define(LOCAL_WRITER, true).
 
 merge(A,B,C, Size, IsLastLevel, Options) ->
-    {ok, BT1} = hanoi_reader:open(A, sequential),
+    {ok, BT1} = hanoi_reader:open(A, [sequential|Options]),
-    {ok, BT2} = hanoi_reader:open(B, sequential),
+    {ok, BT2} = hanoi_reader:open(B, [sequential|Options]),
     case ?LOCAL_WRITER of
         true ->
             {ok, Out} = hanoi_writer:init([C, [{size,Size} | Options]]);

src/hanoi_reader.erl

@@ -40,21 +40,21 @@
 
 -spec open(Name::string()) -> read_file().
 open(Name) ->
-    open(Name, random).
+    open(Name, [random]).
 
--spec open(Name::string(), sequential|random) -> read_file().
+-type config() :: [sequential | random | {atom(), term()}].
 
-%% this is how to open a btree for sequential scanning (merge, fold)
+-spec open(Name::string(), config()) -> read_file().
-open(Name, sequential) ->
-    {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
+open(Name, Config) ->
-open(Name, random) ->
+    case proplists:get_bool(sequential, Config) of
-    {ok, File} = file:open(Name, [read,binary]),
+        true ->
-    open2(Name, File).
+            ReadBufferSize = hanoi:get_opt(read_buffer_size, Config, 512 * 1024),
+            {ok, File} = file:open(Name, [raw,read,{read_ahead, ReadBufferSize},binary]);
+        false ->
+            {ok, File} = file:open(Name, [read,binary])
+    end,
 
-open2(Name, File) ->
     {ok, FileInfo} = file:read_file_info(Name),
 
     %% read root position

src/hanoi_writer.erl

@@ -80,11 +80,12 @@ close(Ref) ->
 init([Name,Options]) ->
 
     Size = proplists:get_value(size, Options, 2048),
+    WriteBufferSize = hanoi:get_opt(write_buffer_size, Options, 512 * 1024),
 
 %    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, BlockSize * 4, 2000}]) of
+                               [raw, exclusive, write, {delayed_write, WriteBufferSize, 2000}]) of
         {ok, IdxFile} ->
             {ok, BloomFilter} = ebloom:new(erlang:min(Size,16#ffffffff), 0.01, 123),
             {ok, #state{ name=Name,

src/riak_kv_hanoi_backend.erl

@@ -103,7 +103,7 @@ start(Partition, Config) ->
                 ok ->
                     case get_data_dir(DataRoot, integer_to_list(Partition)) of
                         {ok, DataDir} ->
-                            case hanoi:open(DataDir) of
+                            case hanoi:open(DataDir, Config) of
                                 {ok, Tree} ->
                                     {ok, #state{tree=Tree, partition=Partition}};
                                 {error, OpenReason}=OpenError ->