Commit 53954671 authored Jan 17, 2014 by Paul E. McKenney

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>

parent 0ae3f73a

tools/testing/selftests/rcutorture/bin/kvm.sh

+36 −1

Original line number	Original line	Diff line number	Diff line
	@@ -214,7 +214,42 @@ do
	done		done
	sort -k2nr $T/cfgcpu > $T/cfgcpu.sort		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/$kversion/" \		-v CONFIGDIR="$CONFIGFRAG/$kversion/" \
	-v KVM="$KVM" \		-v KVM="$KVM" \
	-v ncpus=$cpus \		-v ncpus=$cpus \