On Tue, Dec 14, 2010 at 12:03:05PM -0500, Mark Howison wrote: > On Tue, Dec 14, 2010 at 8:08 AM, Quincey Koziol <[email protected]> wrote: > >> If not, there is another optimization that I think was reported in a > >> paper on PLFS or Adios about passing a flag to the fopen call on each > >> MPI task that tells it not to update the creation/modification time > >> except on the root task. This can greatly reduce the load on the > >> metadata server for a parallel file system. > > > > Interesting, can you send me a reference for this? > > I'm pretty sure the trick was to use O_NOATIME in the open() call, > except on task 0. (You can find this on NICS webpage on I/O best > practices.)
neat trick. Can definitely see how this might help Lustre. Not sure if it will help GPFS or PVFS as much. Hope you find that PDF! This sort of trick definitely belongs in the MPI-IO library, but O_NOATIME on my system is protected by "#ifdef __USE_GNU". For the sake of portability, we try to avoid non-standard flags in MPI land, but this optimization is easy and presumably worthwhile so I'll ask our hard-nosed "portability guys" how we can use this. ==rob -- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA _______________________________________________ Hdf-forum is for HDF software users discussion. [email protected] http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
