Update the MANIFEST and release_docs/RELEASE files

1 files changed, 25 insertions, 0 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index d0de3ee..ed1b6cc 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -62,6 +62,31 @@ New Features
 
     Parallel Library:
     -----------------
+    - Optimize parallel open/location of the HDF5 super-block
+
+      Previous releases of PHDF5 allow all parallel ranks to
+      read the starting elements in a file to validate and process
+      the HDF5 super-block.  As this is accomplished more or less as
+      a synchronous operation, a large number of processes will
+      likely experience a slowdown due to filesystem contention.
+
+      As a first step in improving the startup/file-open performance,
+      we allow MPI rank 0 of the associated MPI communicator to locate
+      the base offset of the super-block and then broadcast that result
+      to the remaining ranks in the parallel group.  Note that this
+      approach is utilized ONLY during file opens which employ the MPIO
+      file driver in HDF5 by previously having called H5Pset_fapl_mpio().
+
+      HDF5 parallel file operations which do not employ multiple ranks
+      e.g. specifiying MPI_COMM_SELF (whose MPI_Comm_size == 1) 
+      as opposed to MPI_COMM_WORLD, will not be affected by this
+      optimization.  Conversely, parallel file operations on subgroups
+      of MPI_COMM_WORLD are allowed to be run in parallel with each
+      subgroup operating as an independant collection of processes.
+
+      (RAW – 2017/10/10, HDFFV-10294)
+
+
     - Large MPI-IO transfers
 
       Previous releases of PHDF5 would fail when attempting to