[PATCH] Improve performance of large restore commands

[Anton Blanchard <anton@samba.org>]

I noticed a large (100MB) restore took hours to complete. The problem
is target_xfer_partial repeatedly mallocs and memcpys the entire
100MB buffer only to find a small portion of it is actually written.

We already cap reads to 4K, so do that for writes. The testcase that
originally took hours now takes 50 seconds.

--

2013-07-25  Anton Blanchard  <anton@samba.org>

	* target.c (target_write_with_progress): Cap write to 4K

Index: b/gdb/target.c
===================================================================
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -2287,9 +2287,11 @@ target_write_with_progress (struct targe
 
   while (xfered < len)
     {
+      /* Cap the write to 4K */
+      int to_transfer = min(4096, len - xfered);
       LONGEST xfer = target_write_partial (ops, object, annex,
 					   (gdb_byte *) buf + xfered,
-					   offset + xfered, len - xfered);
+					   offset + xfered, to_transfer);
 
       if (xfer == 0)
 	return xfered;