On 06/28/2011 01:17 PM, Andreas Dilger wrote:

Note that you need to be careful with FIEMAP for copying files...  There were
some problems reported to this list with this, if the file was newly written.
It is safest to always pass FIEMAP_FLAG_SYNC before copying the file to ensure
the blocks are mapped to disk.

Thanks!

quoted

The copy has completed.  This is a snipped from top I had saved.  This machine has 4 cores and 8G of ram.  There are 32 threads doing copies.  At any time each has a directory to itself.

    % cpu
0573 root 20 0 7574m 1.9g 1356 S 204.3 24.9 3054:22 java
27702 root 20 0 0 0 0 R 70.5 0.0 689:01.73 flush-253:2
22467 root 20 0 0 0 0 S 22.6 0.0 7:55.98 kworker/3:1
22351 root 20 0 0 0 0 S 21.6 0.0 9:42.58 kworker/1:3
22686 root 20 0 0 0 0 S 21.3 0.0 0:26.19 kworker/2:0
22679 root 20 0 0 0 0 S 13.8 0.0 0:29.14 kworker/0:1
   38 root 20 0 0 0 0 S 9.2 0.0 91:21.19 kswapd0
22700 root 20 0 0 0 0 S 7.9 0.0 0:04.64 kworker/0:0
10566 root 20 0 0 0 0 S 3.6 0.0 17:14.77 jbd2/dm-2-8

If I remember correctly top said that: 97% of time was sys time.  So even the time used by Java was still almost all kernel time.    Only a few megabytes was actually swapped.

Looking at the above, "java" is using by far the most memory/CPU, unless this
program is not just doing the copy?

It does walk down the directory tree.  When it finds a directory it 
creates a new object in the thread work queue for the directory it 
found.  Threads read off the the queue creating directories in the 
destination and copying files to the destination.

You could run oprofile to see where the CPU cycles are being used.

I will do this next time I'm running the copy.

Thanks,
Sean