Re: [Bug-ddrescue] Slowness during recovery

[colo]

Digging up this old message from Rob Terrell.

Is there someone that can assist in helping out with patching it to 1.9? 

I made a modification to main.cc so to support ddrescue's direct mode ("-d") when running on Mac OS X or Darwin systems. It seems to work-- in my test case, without -d a volume copy (with around 300 errors) took more than twice as long.

I don't know enough about configure to make this compile in automatically; just use this to configure with O_DIRECT for Darwin/OSX:

        ./configure CPPFLAGS="-DO_DIRECT -DDARWIN"


Patch against 1.6 pre 2:

@@ -265,8 +265,19 @@
   if( check_identical ( iname, oname ) )
     { show_error( "infile and outfile are identical" ); return 1; }

+#ifdef DARWIN
+  // darwin doesn't support o_direct as an option to open() but

+ // you can turn the cache off for a file descriptor with fnctl and F_NOCACHE

+ const int ides = open( iname, O_RDONLY );

+ if( ides < 0 ) { show_error( "cannot open input file", errno ); return 1; }

+  if( o_direct ) {
+       const int fcntlerr = fcntl( ides, F_NOCACHE, 1 );

+ if( fcntlerr < 0 ) { show_error("cannot disable file caching", errno); return 1;}

+  }
+#else
   const int ides = open( iname, O_RDONLY | o_direct );

if( ides < 0 ) { show_error( "cannot open input file", errno ); return 1; }

+#endif
   const long long isize = lseek( ides, 0, SEEK_END );

if( isize < 0 ) { show_error( "input file is not seekable" ); return 1; }