rcutorture: Do better bin packing

Running the standard set of rcutorture tests on 24 CPUs results in
the following sub-optimal schedule:

	----start batch----
	 TREE07 16
	----start batch----
	 TREE08 16
	 SRCU-P 8
	----start batch----
	 TREE01 8
	 TREE02 8
	 TREE03 8
	----start batch----
	 TREE04 8
	 TREE05 8
	 TREE06 8
	----start batch----
	 SRCU-N 4
	 TINY01 1
	 TINY02 1
	 TREE09 1

If one of the eight-CPU runs were to be moved into the first batch,
the test suite would complete in four batches rather than five.

This commit therefore uses a greedy algorithm to re-order the test
entries so that the sequential batching will produce an optimal schedule
in this case:

	----start batch----
	 TREE07 16
	 SRCU-P 8
	----start batch----
	 TREE08 16
	 TREE01 8
	----start batch----
	 TREE02 8
	 TREE03 8
	 TREE04 8
	----start batch----
	 TREE05 8
	 TREE06 8
	 SRCU-N 4
	 TINY01 1
	 TINY02 1
	 TREE09 1

Please note that this is still not an optimal bin-packing algorithm,
however, it does produce optimal solutions for most common scenarios.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index ad3779cefdb853356eab963524ba04bda6292b6f..18649b87ea6c631d25f06a85e4f55f524223da98 100644 (file)
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -214,7 +214,42 @@ do
 done
 sort -k2nr $T/cfgcpu > $T/cfgcpu.sort
 
-awk < $T/cfgcpu.sort \
+awk < $T/cfgcpu.sort > $T/cfgcpu.pack -v ncpus=$cpus '
+BEGIN {
+       njobs = 0;
+}
+
+{
+       cf[njobs] = $1;
+       cpus[njobs] = $2;
+       njobs++;
+}
+
+END {
+       alldone = 0;
+       batch = 0;
+       nc = -1;
+       while (nc != ncpus) {
+               batch++;
+               nc = ncpus;
+               for (i = 0; i < njobs; i++) {
+                       if (done[i])
+                               continue;
+                       if (nc >= cpus[i] || nc == ncpus) {
+                               done[i] = batch;
+                               nc -= cpus[i];
+                               if (nc <= 0)
+                                       break;
+                       }
+               }
+       }
+       for (b = 1; b <= batch; b++)
+               for (i = 0; i < njobs; i++)
+                       if (done[i] == b)
+                               print cf[i], cpus[i];
+}'
+
+awk < $T/cfgcpu.pack \
        -v CONFIGDIR="$CONFIGFRAG/$kversion/" \
        -v KVM="$KVM" \
        -v ncpus=$cpus \