Some I/O simple benchmarks

MPI_benchmark/compile-command

@@ -1 +1,2 @@
-mpicxx  -fsycl halo_mpi.cc -o halo_mpi
+mpicxx  -fsycl halo_mpi.cc -o halo_mpi
+mpicxx -O2 -std=c++11 io_mpi.cc -o io_mpi

MPI_benchmark/io_frontier.slurm

@@ -0,0 +1,95 @@
+#!/bin/bash -l
+
+# Standalone MPI-only I/O reproducer on Frontier.  No Grid, no accelerator,
+# so no GCD/NUMA wrapper is needed -- the point of the exercise is that this
+# depends on nothing but an MPI installation and a filesystem.
+#
+#   mpicxx -O2 -std=c++11 io_mpi.cc -o io_mpi
+#
+# Weak scan: the local volume, and therefore the file view structure, is held
+# identical at every rung and only the number of Lustre clients changes:
+#
+#   local volume  8.8.32.128 = 262144 sites x 576 B = 151 MB/rank
+#   file view     32768 contiguous runs of 4608 B per rank, at every rung
+#   aggregate     k=2, row of 16, 8 extents of 18 MB, at every rung
+#
+# so any change in the relative bandwidth of the two lexicographic paths is a
+# property of the client count alone.
+
+#SBATCH --job-name=ioMPI
+#SBATCH --nodes=128
+#SBATCH --ntasks-per-node=8
+#SBATCH --cpus-per-task=7
+#SBATCH --time=02:00:00
+#SBATCH --account=phy157_dwf
+#SBATCH --exclusive
+#SBATCH --mem=0
+
+module load cce/21.0.0
+module load cpe/26.03
+
+WORK=/lustre/orion/phy157/proj-shared/phy157_dwf/paboyle/iompi.$SLURM_JOB_ID
+mkdir -p $WORK
+cd       $WORK
+
+# Do NOT stripe by default.  Wide striping is what rescues the collective at
+# scale and costs every other path a factor of 1.2-2.2; the default layout is
+# what a user gets without knowing to ask.  Uncomment to reproduce that
+# interaction, and record which one you ran.
+#lfs setstripe -c -1 -S 8M $WORK
+lfs getstripe -d $WORK
+
+BIN=$SLURM_SUBMIT_DIR/io_mpi
+ARGS="--target 4194304 --reps 3"
+
+# ROMIO's own view of what it did.  Verbose, but the first thing anyone
+# reading the report will ask for.
+# export MPICH_MPIIO_STATS=1
+# export MPICH_MPIIO_TIMERS=1
+
+run () {   # run <nodes> <grid> <mpi> <comment> [extra args...]
+  local nodes=$1 gr=$2 mp=$3 note=$4
+  local nranks=$(( nodes * 8 ))
+  shift 4
+  echo
+  echo "==================================================================="
+  echo "=== nodes=$nodes ranks=$nranks grid=$gr mpi=$mp   $note"
+  echo "=== extra: $@"
+  echo "==================================================================="
+  srun -N$nodes -n$nranks --ntasks-per-node=8 $BIN --grid $gr --mpi $mp $ARGS "$@"
+  echo "=== exit $?"
+}
+
+#####################################################################
+# Phase 0.  Correctness, including the non-uniform Alltoallv branch
+# (odd process factor in an un-split dimension).  Small, and the
+# whole-file crc32 is serial, so keep the volume down here.
+#####################################################################
+run 1 12.12.8.8   2.2.2.1  "correctness, uniform counts"     --reps 0 --serial-crc
+run 3 24.12.8.8   3.2.2.2  "correctness, NON-uniform counts" --reps 0 --serial-crc
+run 4 16.16.16.32 2.2.2.4  "correctness, non-zero offset"    --reps 0 --serial-crc --offset 1024
+
+#####################################################################
+# Phase 1.  Weak scan, 151 MB/rank.  Timing only.
+#####################################################################
+run    4     32.32.64.128    4.4.2.1   "4.8 GB"    --no-validate
+run    8     32.32.64.256    4.4.2.2   "9.7 GB"    --no-validate
+run   16     32.32.64.512    4.4.2.4   "19.3 GB"   --no-validate
+run   32     32.32.128.512   4.4.4.4   "38.6 GB"   --no-validate
+run   64     32.32.128.1024  4.4.4.8   "77.3 GB"   --no-validate
+run  128     32.32.256.1024  4.4.8.8   "154.6 GB"  --no-validate
+
+#####################################################################
+# Phase 2.  Answer the two questions a reviewer will ask immediately.
+#####################################################################
+# Is the gap an artefact of measuring cache rather than the filesystem?
+run  128     32.32.256.1024  4.4.8.8   "154.6 GB, durable"  --no-validate --fsync --drop-cache
+# Does the collective recover if it is given the hints it wants?
+run  128     32.32.256.1024  4.4.8.8   "154.6 GB, cb hints" --no-validate \
+     --hints romio_cb_write=enable,romio_cb_read=enable,cb_nodes=128,cb_buffer_size=16777216
+# Does the degenerate memory subarray matter?
+run  128     32.32.256.1024  4.4.8.8   "154.6 GB, mem subarray" --no-validate --mem-subarray
+
+echo
+echo "=== done.  Files left in $WORK"
+ls -l $WORK