Hi all,
When I used parellel hdf5 write speed with 4 process(collective) and 1 process , the results surprised me, the speed of 1 process is even faster than 4 process. I have noticed that when writing data with 4 process, the cpu use ratio drop to about 70% ~ %10, the last cpu seems to be has the minimal efficiency.
It is obviously reasonale, any one has expericece about this, Could you give me some suggestion, and I will check my code carefully.
Thanks in advance.
tony
Hi. What file system are you writing to? If you are writing to NFS,
you won't see much speedup with more clients. Are you using HDF5 in
MPI-IO mode, or are you using posix? I think MPI-IO will give you
better performance, especially if you are using hyperslabs.
==rob
On Wed, Aug 26, 2009 at 11:10:46PM +0800, 4 wrote:
When I used parellel hdf5 write speed with 4 process(collective) and 1 process , the results surprised me, the speed of 1 process is even faster than 4 process. I have noticed that when writing data with 4 process, the cpu use ratio drop to about 70% ~ %10, the last cpu seems to be has the minimal efficiency.
It is obviously reasonale, any one has expericece about this, Could you give me some suggestion, and I will check my code carefully.
--
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA
