From fce3d60ef3fb3d83f7d5a2ab050fb344ae641986 Mon Sep 17 00:00:00 2001
From: Jesper Louis Andersen <jesper.louis.andersen@gmail.com>
Date: Thu, 31 Jul 2008 00:00:33 +0200
Subject: [PATCH] Optimize the dirwatcher, change its check time to 20 seconds.

There is nothing more to do here right now. The main problem is
that regexp is hellishly slow and out of the time spent waiting
over 120 seconds (invocation every 5th) 15 seconds were spent
in regexp parsing of files. I seriously think we can gain something
by just eating *every* file and scan it ourselves with a function.
---
 lib/etorrent-1.0/src/etorrent_dirwatcher.erl | 65 ++++++++++++++++++----------
 1 file changed, 41 insertions(+), 24 deletions(-)

diff --git a/lib/etorrent-1.0/src/etorrent_dirwatcher.erl b/lib/etorrent-1.0/src/etorrent_dirwatcher.erl
index bcc10da..1366994 100644
--- a/lib/etorrent-1.0/src/etorrent_dirwatcher.erl
+++ b/lib/etorrent-1.0/src/etorrent_dirwatcher.erl
@@ -19,9 +19,8 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
 	 terminate/2, code_change/3]).
 
--record(state, {dir = none,
-	        fileset = none}).
--define(WATCH_WAIT_TIME, 5000).
+-record(state, {dir = none}).
+-define(WATCH_WAIT_TIME, timer:seconds(20)).
 -define(SERVER, ?MODULE).
 
 %%====================================================================
@@ -42,11 +41,9 @@ dir_watched() ->
 %%====================================================================
 init([]) ->
     {ok, Dir} = application:get_env(etorrent, dir),
-    % Provide a timeout in 100 ms to get up fast
-    {ok, #state{dir = Dir, fileset = sets:new()}, 100}.
+    _Tid = ets:new(etorrent_dirwatcher, [named_table, protected]),
+    {ok, #state{dir = Dir}, 0}.
 
-handle_call(report_on_files, _Who, S) ->
-    {reply, sets:to_list(S#state.fileset), S, ?WATCH_WAIT_TIME};
 handle_call(dir_watched, _Who, S) ->
     {reply, S#state.dir, S, ?WATCH_WAIT_TIME};
 handle_call(_Request, _From, State) ->
@@ -57,8 +54,8 @@ handle_cast(_Request, S) ->
     {noreply, S, ?WATCH_WAIT_TIME}.
 
 handle_info(timeout, S) ->
-    N = watch_directories(S),
-    {noreply, N, ?WATCH_WAIT_TIME};
+    watch_directories(S),
+    {noreply, S, ?WATCH_WAIT_TIME};
 handle_info(_Info, State) ->
     {noreply, State, ?WATCH_WAIT_TIME}.
 
@@ -74,18 +71,38 @@ code_change(_OldVsn, State, _Extra) ->
 
 %% Operations
 watch_directories(S) ->
-    {ok, A, R, N} = scan_files_in_dir(S),
-    lists:foreach(fun(F) -> etorrent_mgr:start(F) end,
-		  sets:to_list(A)),
-    lists:foreach(fun(F) -> etorrent_mgr:stop(F) end,
-		  sets:to_list(R)),
-    N.
-
-scan_files_in_dir(S) ->
-    Files = filelib:fold_files(S#state.dir, ".*\.torrent", false,
-			       fun(F, Accum) -> [F | Accum] end, []),
-    FilesSet = sets:from_list(Files),
-    Added = sets:subtract(FilesSet, S#state.fileset),
-    Removed = sets:subtract(S#state.fileset, FilesSet),
-    NewState = S#state{fileset = FilesSet},
-    {ok, Added, Removed, NewState}.
+    reset_marks(ets:first(etorrent_dirwatcher)),
+    F = fun(F, ok) ->
+		process_file(F),
+		ok
+	end,
+    ok = filelib:fold_files(S#state.dir, ".*\.torrent", false,
+				F, ok),
+    ets:safe_fixtable(etorrent_dirwatcher, true),
+    start_stop(ets:first(etorrent_dirwatcher)),
+    ets:safe_fixtable(etorrent_dirwatcher, false),
+    ok.
+
+process_file(F) ->
+    case ets:lookup(etorrent_dirwatcher, F) of
+	[] ->
+	    ets:insert(etorrent_dirwatcher, {F, new});
+	[_] ->
+	    ets:insert(etorrent_dirwatcher, {F, marked})
+    end.
+
+reset_marks('$end_of_table') -> ok;
+reset_marks(Key) ->
+    ets:insert(etorrent_dirwatcher, {Key, unmarked}),
+    reset_marks(ets:next(etorrent_dirwatcher, Key)).
+
+start_stop('$end_of_table') -> ok;
+start_stop(Key) ->
+    [{Key, S}] = ets:lookup(etorrent_dirwatcher, Key),
+    case S of
+	new -> etorrent_mgr:start(Key);
+	marked -> ok;
+	unmarked -> etorrent_mgr:stop(Key),
+		    ets:delete(etorrent_dirwatcher, Key)
+    end,
+    start_stop(ets:next(etorrent_dirwatcher, Key)).
-- 
2.11.4.GIT