as with lustre, pread/pwrtie need a feature level newer than
--enable-strict requests.  autoconf already checked for the function at
configure time, so we know it's there.  TODO: more robust autoconf
checks and provide a "my_pwrite" that wraps lseek/write for a fallback.

Paul Coffman authored Mar 21, 2014 and Rob Latham committed Mar 26, 2014

reconfiguration changes from bg to gpfs with platformspec; removal of
lockless

Useful for situations like evaluating various collective I/O approaches.
Reading/writing /dev/null eliminates file system variablity.

bluegene timer code had two "levels" of timing.  that seemed kind of
pointless so lump it all into one level.

this "new" system call (part of POSIX-2001) saves us a system call on
Blue Gene.  Seems to get us back 5 seconds for one workload at small
(half rack) scales.

bglockles uses the common read/write routines for contig read/wrties, so
bluegene timing infrastrucutre wasn't actually timing anything.  Since
this introduces blue gene bits into common code, please do not merge to
master.  Instead, we should rework all the timing bits so that it no
longer times "bluegene" but rather all of ROMIO.  Furthermore, the
locky bits of 'bg:' driver should be yanked anyway, obviating the need
for bglockless.

MPI-3 introduced MPI_Count and MPI_Type_size_x.  Use these new routines
throughout ROMIO to support large datatypes.

Still to do:
- update other ADIO drivers

Signed-off-by: Pavan Balaji <balaji@mcs.anl.gov>

It would appear that we can get more than two gigs worth of data down to
the write(2) and read(2) system call, but those syscalls fail to process
all of it.  Perfectly valid behavior for unix to return less than
requested, but until now, ROMIO never dealt with it.

Still to do: update Blue Gene drivers

closes ticket #1742  , since that ticket is only asking about I/O to
less than two gigs.  Lots and Lots more work needed for larger than two
gigs.

Haizhu Liu authored May 01, 2013 and Rob Latham committed May 14, 2013

(ibm) D190161
(ibm) 55566af07e7d69df17005e50c783ff3ae26cc325

Signed-off-by: Michael Blocksome <blocksom@us.ibm.com>

By setting "indent-tabs-mode:nil" we should hopefully begin to slowly
squeeze out hard tabs from the source without a disruptive (to
downstream projects) whitespace-fixing change.

No reviewer.

now) unless enabled with a hint.