Author: fdmanana
Date: Thu Nov 11 00:59:40 2010
New Revision: 1033790
URL: http://svn.apache.org/viewvc?rev=1033790&view=rev
Log:
Micro optimization: when reading an iolist, read up to 8Kbs instead of the 4
bytes length prefix only in the first file read operation.
For reads of small terms/iolist (up to 8Kbs), this speeds up the whole
operation. No impact on larger terms/iolists.
Modified:
couchdb/trunk/src/couchdb/couch_file.erl
couchdb/trunk/test/etap/010-file-basics.t
Modified: couchdb/trunk/src/couchdb/couch_file.erl
URL:
http://svn.apache.org/viewvc/couchdb/trunk/src/couchdb/couch_file.erl?rev=1033790&r1=1033789&r2=1033790&view=diff
==============================================================================
--- couchdb/trunk/src/couchdb/couch_file.erl (original)
+++ couchdb/trunk/src/couchdb/couch_file.erl Thu Nov 11 00:59:40 2010
@@ -283,20 +283,28 @@ terminate(_Reason, #file{fd = Fd}) ->
handle_call({pread_iolist, Pos}, _From, File) ->
- {LenIolist, NextPos} = read_raw_iolist_int(File, Pos, 4),
- case iolist_to_binary(LenIolist) of
- <<1:1/integer,Len:31/integer>> -> % an MD5-prefixed term
- {Md5AndIoList, _} = read_raw_iolist_int(File, NextPos, Len+16),
- {Md5, IoList} = extract_md5(Md5AndIoList),
+ {RawData, NextPos} = try
+ % up to 8Kbs of read ahead
+ read_raw_iolist_int(File, Pos, 2 * ?SIZE_BLOCK - (Pos rem ?SIZE_BLOCK))
+ catch
+ _:_ ->
+ read_raw_iolist_int(File, Pos, 4)
+ end,
+ <<Prefix:1/integer, Len:31/integer, RestRawData/binary>> =
+ iolist_to_binary(RawData),
+ case Prefix of
+ 1 ->
+ {Md5, IoList} = extract_md5(
+ maybe_read_more_iolist(RestRawData, 16 + Len, NextPos, File)),
case couch_util:md5(IoList) of
Md5 ->
{reply, {ok, IoList}, File};
_ ->
{stop, file_corruption, {error,file_corruption}, File}
end;
- <<0:1/integer,Len:31/integer>> ->
- {Iolist, _} = read_raw_iolist_int(File, NextPos, Len),
- {reply, {ok, Iolist}, File}
+ 0 ->
+ IoList = maybe_read_more_iolist(RestRawData, Len, NextPos, File),
+ {reply, {ok, IoList}, File}
end;
handle_call({pread, Pos, Bytes}, _From,
#file{fd=Fd,tail_append_begin=TailAppendBegin}=File) ->
{ok, Bin} = file:pread(Fd, Pos, Bytes),
@@ -503,6 +511,15 @@ load_header(Fd, Block) ->
Md5Sig = couch_util:md5(HeaderBin),
{ok, HeaderBin}.
+maybe_read_more_iolist(Buffer, DataSize, _, _)
+ when DataSize =< byte_size(Buffer) ->
+ <<Data:DataSize/binary, _/binary>> = Buffer,
+ [Data];
+maybe_read_more_iolist(Buffer, DataSize, NextPos, File) ->
+ {Missing, _} =
+ read_raw_iolist_int(File, NextPos, DataSize - byte_size(Buffer)),
+ [Buffer, Missing].
+
-spec read_raw_iolist_int(#file{}, Pos::non_neg_integer(),
Len::non_neg_integer()) ->
{Data::iolist(), CurPos::non_neg_integer()}.
read_raw_iolist_int(Fd, {Pos, _Size}, Len) -> % 0110 UPGRADE CODE
Modified: couchdb/trunk/test/etap/010-file-basics.t
URL:
http://svn.apache.org/viewvc/couchdb/trunk/test/etap/010-file-basics.t?rev=1033790&r1=1033789&r2=1033790&view=diff
==============================================================================
--- couchdb/trunk/test/etap/010-file-basics.t (original)
+++ couchdb/trunk/test/etap/010-file-basics.t Thu Nov 11 00:59:40 2010
@@ -84,7 +84,8 @@ test() ->
% append_binary == append_iolist?
% Possible bug in pread_iolist or iolist() -> append_binary
{ok, IOLPos} = couch_file:append_binary(Fd, ["foo", $m, <<"bam">>]),
- etap:is({ok, [<<"foombam">>]}, couch_file:pread_iolist(Fd, IOLPos),
+ {ok, IoList} = couch_file:pread_iolist(Fd, IOLPos),
+ etap:is(<<"foombam">>, iolist_to_binary(IoList),
"Reading an results in a binary form of the written iolist()"),
% XXX: How does on test fsync?
