On Fri, Dec 11, 2009 at 10:58:19AM -0800, Mark Howison wrote: > The purple indicates ftruncate, which is only called from task 0 (that > is how MPI_File_set_size is implemented). The salmon at the far right > actually indicates fsyncs, not reads. And the brown (hard to see) is > fclose.
Just to add a bit of ROMIO MPI-IO background while you explore this: In the old days every MPI process called ftruncate, and of course that gave brutally poor performance. This "ftruncate from one" approach has been in place since 2004. I would be both shocked and appalled if you encountered an ancient ROMIO-based MPI-IO implementation that still does ftruncate from all. if you are nfs-exporting this lustre volume for some reason, ROMIO will behave quite differently (and slowly). But you aren't doing that or you'd see a very different IPM graph. ==rob -- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
