pkg/fuzzer: optimize smash jobs

1. Run only 25 mutations during smash.
2. Run collide during normal fuzzing rather than during smashing.
3. Run hints and fault injection before random mutations
   and order hints/fault injection jobs.
4. Random mutations still run round-robin w/o ordering
   to give better diversity.

3 files changed, 36 insertions, 28 deletions

diff --git a/pkg/fuzzer/fuzzer.go b/pkg/fuzzer/fuzzer.go
index 5b95f4eec..09ce69c00 100644
--- a/pkg/fuzzer/fuzzer.go
+++ b/pkg/fuzzer/fuzzer.go
@@ -67,10 +67,10 @@ func NewFuzzer(ctx context.Context, cfg *Config, rnd *rand.Rand,
 }
 
 type execQueues struct {
-	smashQueue           *queue.PlainQueue
-	triageQueue          *queue.DynamicOrderer
-	candidateQueue       *queue.PlainQueue
 	triageCandidateQueue *queue.DynamicOrderer
+	candidateQueue       *queue.PlainQueue
+	triageQueue          *queue.DynamicOrderer
+	smashQueue           *queue.PlainQueue
 	source               queue.Source
 }
 
@@ -229,6 +229,12 @@ func (fuzzer *Fuzzer) genFuzz() *queue.Request {
 	if req == nil {
 		req = genProgRequest(fuzzer, rnd)
 	}
+	if fuzzer.Config.Collide && rnd.Intn(3) == 0 {
+		req = &queue.Request{
+			Prog: randomCollide(req.Prog, rnd),
+			Stat: fuzzer.statExecCollide,
+		}
+	}
 	fuzzer.prepare(req, 0, 0)
 	return req
 }
diff --git a/pkg/fuzzer/job.go b/pkg/fuzzer/job.go
index 0268172a9..d1397c5b2 100644
--- a/pkg/fuzzer/job.go
+++ b/pkg/fuzzer/job.go
@@ -123,8 +123,21 @@ func (job *triageJob) handleCall(call int, info *triageCall) {
 		job.fuzzer.startJob(job.fuzzer.statJobsSmash, &smashJob{
 			exec: job.fuzzer.smashQueue,
 			p:    p.Clone(),
-			call: call,
 		})
+		if job.fuzzer.Config.Comparisons && call >= 0 {
+			job.fuzzer.startJob(job.fuzzer.statJobsHints, &hintsJob{
+				exec: job.fuzzer.smashQueue,
+				p:    p.Clone(),
+				call: call,
+			})
+		}
+		if job.fuzzer.Config.FaultInjection && call >= 0 {
+			job.fuzzer.startJob(job.fuzzer.statJobsFaultInjection, &faultInjectionJob{
+				exec: job.fuzzer.smashQueue,
+				p:    p.Clone(),
+				call: call,
+			})
+		}
 	}
 	job.fuzzer.Logf(2, "added new input for %v to the corpus: %s", callName, p)
 	input := corpus.NewInput{
@@ -301,15 +314,8 @@ type smashJob struct {
 
 func (job *smashJob) run(fuzzer *Fuzzer) {
 	fuzzer.Logf(2, "smashing the program %s (call=%d):", job.p, job.call)
-	if fuzzer.Config.Comparisons && job.call >= 0 {
-		fuzzer.startJob(fuzzer.statJobsHints, &hintsJob{
-			exec: fuzzer.smashQueue,
-			p:    job.p.Clone(),
-			call: job.call,
-		})
-	}
 
-	const iters = 75
+	const iters = 25
 	rnd := fuzzer.rand()
 	for i := 0; i < iters; i++ {
 		p := job.p.Clone()
@@ -325,18 +331,6 @@ func (job *smashJob) run(fuzzer *Fuzzer) {
 		if result.Stop() {
 			return
 		}
-		if fuzzer.Config.Collide {
-			result := fuzzer.execute(job.exec, &queue.Request{
-				Prog: randomCollide(p, rnd),
-				Stat: fuzzer.statExecCollide,
-			})
-			if result.Stop() {
-				return
-			}
-		}
-	}
-	if fuzzer.Config.FaultInjection && job.call >= 0 {
-		job.faultInjection(fuzzer)
 	}
 }
 
@@ -362,7 +356,13 @@ func randomCollide(origP *prog.Prog, rnd *rand.Rand) *prog.Prog {
 	return p
 }
 
-func (job *smashJob) faultInjection(fuzzer *Fuzzer) {
+type faultInjectionJob struct {
+	exec queue.Executor
+	p    *prog.Prog
+	call int
+}
+
+func (job *faultInjectionJob) run(fuzzer *Fuzzer) {
 	for nth := 1; nth <= 100; nth++ {
 		fuzzer.Logf(2, "injecting fault into call %v, step %v",
 			job.call, nth)
diff --git a/pkg/fuzzer/stats.go b/pkg/fuzzer/stats.go
index a5df691df..db2dfd3b3 100644
--- a/pkg/fuzzer/stats.go
+++ b/pkg/fuzzer/stats.go
@@ -12,6 +12,7 @@ type Stats struct {
 	statJobsTriage          *stats.Val
 	statJobsTriageCandidate *stats.Val
 	statJobsSmash           *stats.Val
+	statJobsFaultInjection  *stats.Val
 	statJobsHints           *stats.Val
 	statExecTime            *stats.Val
 	statExecGenerate        *stats.Val
@@ -36,9 +37,10 @@ func newStats() Stats {
 		statJobsTriage: stats.Create("triage jobs", "Running triage jobs", stats.StackedGraph("jobs")),
 		statJobsTriageCandidate: stats.Create("candidate triage jobs", "Running candidate triage jobs",
 			stats.StackedGraph("jobs")),
-		statJobsSmash: stats.Create("smash jobs", "Running smash jobs", stats.StackedGraph("jobs")),
-		statJobsHints: stats.Create("hints jobs", "Running hints jobs", stats.StackedGraph("jobs")),
-		statExecTime:  stats.Create("prog exec time", "Test program execution time (ms)", stats.Distribution{}),
+		statJobsSmash:          stats.Create("smash jobs", "Running smash jobs", stats.StackedGraph("jobs")),
+		statJobsFaultInjection: stats.Create("fault jobs", "Running fault injection jobs", stats.StackedGraph("jobs")),
+		statJobsHints:          stats.Create("hints jobs", "Running hints jobs", stats.StackedGraph("jobs")),
+		statExecTime:           stats.Create("prog exec time", "Test program execution time (ms)", stats.Distribution{}),
 		statExecGenerate: stats.Create("exec gen", "Executions of generated programs", stats.Rate{},
 			stats.StackedGraph("exec")),
 		statExecFuzz: stats.Create("exec fuzz", "Executions of mutated programs",