# HG changeset patch
# User David Scott <dave.scott@xxxxxxxxxxxxx>
# Date 1279905520 -3600
# Node ID 3bf70773971b9906e4d7355049b2cf7a88a13b23
# Parent  2580868fdc435e5c729f98bd707d018dafd3dc2a
CA-43021: hook in 'sparse_dd' for improved VM.copy performance

On local LVHD, VM.copies of freshly installed guests are much quicker:

Guest	       Previous VM.copy time	New VM.copy time   Speedup
----------------------------------------------------------------
Debian Lenny   2:11                     1:18               40%
Windows 7      14:18                    7:57               44%

Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>

diff -r 2580868fdc43 -r 3bf70773971b ocaml/xapi/sm_fs_ops.ml
--- a/ocaml/xapi/sm_fs_ops.ml	Fri Jul 23 18:18:39 2010 +0100
+++ b/ocaml/xapi/sm_fs_ops.ml	Fri Jul 23 18:18:40 2010 +0100
@@ -138,59 +138,48 @@
 	      raise e
 	  )
 	  
-exception Cancelled
-exception NonZero
-
-(* dd with sparseness check *)
-let sparse_dd refresh_session ~__context sparse ifd ofd size bs =
-  let round v = int_of_float (v *. 50.0) in
-  let update = 
-    let oldvalue = ref (-1.0) in
-    fun value ->  
-      if round value <> round !oldvalue then begin
-	TaskHelper.exn_if_cancelling ~__context;
-	TaskHelper.operate_on_db_task ~__context 
-	  (fun self -> 
-	    Db.Task.set_progress ~__context ~self ~value);
-      end;
-      oldvalue := value
-  in
-
-  let buf = String.create bs in
-  
-  let allzero s n =
-    try
-      for i=0 to n-1 do
-        if s.[i] <> '\000' then raise NonZero
-      done;
-      true
-    with NonZero -> false
-  in
-
-  let rec do_block offset =
-    refresh_session ();
-
-    update ((Int64.to_float offset) /. (Int64.to_float size));   
-    let remaining = Int64.sub size offset in
-    if remaining=0L 
-    then ()  (* EOF *)
-    else
-      begin
-	let this_chunk = Int64.to_int (min remaining (Int64.of_int bs)) in
-	Unixext.really_read ifd buf 0 this_chunk;
-	begin
-	  if sparse && (allzero buf this_chunk)
-          then
-	    ignore(Unix.LargeFile.lseek ofd (Int64.of_int this_chunk) Unix.SEEK_CUR)
-	  else
-	    let n = Unix.write ofd buf 0 this_chunk in
-	    (if n<this_chunk then failwith "Error!")
-	end;
-	do_block (Int64.add offset (Int64.of_int this_chunk))
-      end
-  in
-  do_block 0L;
-  update 1.0
+(** Use the new external sparse_dd program *)
+let sparse_dd_new ~__context prezeroed infile outfile size = 
+	let pipe_read, pipe_write = Unix.pipe () in
+	let to_close = ref [ pipe_read; pipe_write ] in
+	let close x = if List.mem x !to_close then (Unix.close x; to_close := List.filter (fun y -> y <> x) !to_close) in
+	finally
+	(fun () ->
+		match Forkhelpers.with_logfile_fd "sparse_dd"
+			(fun log_fd ->
+				let pid = Forkhelpers.safe_close_and_exec None (Some pipe_write) (Some log_fd) [] 
+				"/opt/xensource/libexec/sparse_dd"
+				([ "-machine"; "-src"; infile; "-dest"; outfile; "-size"; Int64.to_string size ] @
+				(if prezeroed then [ "-prezeroed" ] else [])) in
+				close pipe_write;
+				(* Read Progress: output from the binary *)
+				let buf = String.create 128 in
+				let finished = ref false in
+				while not (!finished) do
+					let n = Unix.read pipe_read buf 0 (String.length buf) in
+					if n = 0 then finished := true else debug "sparse_dd: %s" (String.sub buf 0 n);
+					try 
+						Scanf.sscanf (String.sub buf 0 n) "Progress: %d"
+						(fun progress ->
+							TaskHelper.exn_if_cancelling ~__context;
+							TaskHelper.operate_on_db_task ~__context 
+		  					(fun self -> Db.Task.set_progress ~__context ~self ~value:(float_of_int progress /. 100.))
+						)
+					with _ -> ()
+				done;
+				match Forkhelpers.waitpid pid with
+				| (_, Unix.WEXITED 0) -> ()
+				| (_, Unix.WEXITED n) -> error "sparse_dd exit: %d" n; failwith "sparse_dd"
+			) with
+		| Forkhelpers.Success _ -> ()
+		| Forkhelpers.Failure (log, exn) ->
+			error "Failure from sparse_dd: %s" log;
+			raise exn	
+	)
+	(fun () ->
+		close pipe_read;
+		close pipe_write)
+	
 
 (* SCTX-286: thin provisioning is thrown away over VDI.copy, VM.import(VM.export).
    Return true if the newly created vdi must have zeroes written into it; default to false
@@ -226,38 +215,18 @@
 let copy_vdi ~__context vdi_src vdi_dst = 
   TaskHelper.set_cancellable ~__context;
   Helpers.call_api_functions ~__context (fun rpc session_id ->
-  let refresh_session = Xapi_session.consider_touching_session rpc session_id in
 
 
   (* Use the sparse copy unless we must write zeroes into the new VDI *)
   let sparse = not (must_write_zeroes_into_new_vdi ~__context vdi_dst) in
 
   let size = Db.VDI.get_virtual_size ~__context ~self:vdi_src in
-  let blocksize = 1024*1024 in
-
-  debug "Sm_fs_ops.copy_vdi: copying %Ld in blocks of %d%s preserving sparseness" size blocksize (if sparse then "" else " NOT");
-
-  let dd = sparse_dd refresh_session ~__context sparse in
 
   with_block_attached_device __context rpc session_id vdi_src `RO
     (fun device_src ->
        with_block_attached_device __context rpc session_id vdi_dst `RW
 	 (fun device_dst ->
-	    let ifd=Unix.openfile device_src [Unix.O_RDONLY] 0o600 
-	    and ofd=Unix.openfile device_dst [Unix.O_WRONLY; Unix.O_SYNC] 0o600 in
-	    finally
-	      (fun () ->
-		 try
-		   dd ifd ofd size blocksize;
-		 with
-		   | Unix.Unix_error(Unix.EIO, _, _) ->
-		       raise (Api_errors.Server_error (Api_errors.vdi_io_error, ["Device I/O error"]))
-		   | e ->
-		       debug "Caught exception %s" (ExnHelper.string_of_exn e);
-		       log_backtrace ())
-	      (fun () ->
-		 Unix.close ifd;
-		 Unix.close ofd)
+	    sparse_dd_new ~__context sparse device_src device_dst size; 
 	 )
     )
   )