5 files changed, 44 insertions, 33 deletions
diff --git a/internal/statsengine/bench_test.go b/internal/statsengine/bench_test.go
index 646bdda..99d5c87 100644
--- a/internal/statsengine/bench_test.go
+++ b/internal/statsengine/bench_test.go
@@ -1,7 +1,7 @@
 package statsengine
 
 import (
-	"math/rand"
+	"math/rand/v2"
 	"testing"
 	"time"
 
@@ -9,7 +9,7 @@ import (
 )
 
 func BenchmarkSyscallAccumulatorSnapshot(b *testing.B) {
-	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewSource(123)))
+	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewPCG(123, 0)))
 	traceIDs := []types.TraceId{
 		types.SYS_ENTER_READ,
 		types.SYS_ENTER_WRITE,
diff --git a/internal/statsengine/filerank.go b/internal/statsengine/filerank.go
index dd83e8d..d24ab93 100644
--- a/internal/statsengine/filerank.go
+++ b/internal/statsengine/filerank.go
@@ -1,8 +1,9 @@
 package statsengine
 
 import (
+	"cmp"
 	"container/heap"
-	"sort"
+	"slices"
 
 	"ior/internal/event"
 	"ior/internal/types"
@@ -123,11 +124,11 @@ func buildFileSnapshots(inputs []fileSnapshotInput) []FileSnapshot {
 	for _, in := range inputs {
 		out = append(out, in.toSnapshot())
 	}
-	sort.Slice(out, func(i, j int) bool {
-		if out[i].Accesses != out[j].Accesses {
-			return out[i].Accesses > out[j].Accesses
+	slices.SortFunc(out, func(a, b FileSnapshot) int {
+		if a.Accesses != b.Accesses {
+			return cmp.Compare(b.Accesses, a.Accesses)
 		}
-		return out[i].Path < out[j].Path
+		return cmp.Compare(a.Path, b.Path)
 	})
 	return out
 }
diff --git a/internal/statsengine/process.go b/internal/statsengine/process.go
index b00a4bb..3bfd019 100644
--- a/internal/statsengine/process.go
+++ b/internal/statsengine/process.go
@@ -1,7 +1,8 @@
 package statsengine
 
 import (
-	"sort"
+	"cmp"
+	"slices"
 	"time"
 
 	"ior/internal/event"
@@ -115,14 +116,14 @@ func buildProcessSnapshots(inputs []processSnapshotInput, elapsed time.Duration)
 	for _, in := range inputs {
 		result = append(result, in.toSnapshot(rateDiv))
 	}
-	sort.Slice(result, func(i, j int) bool {
-		if result[i].Syscalls != result[j].Syscalls {
-			return result[i].Syscalls > result[j].Syscalls
+	slices.SortFunc(result, func(a, b ProcessSnapshot) int {
+		if a.Syscalls != b.Syscalls {
+			return cmp.Compare(b.Syscalls, a.Syscalls)
 		}
-		if result[i].Bytes != result[j].Bytes {
-			return result[i].Bytes > result[j].Bytes
+		if a.Bytes != b.Bytes {
+			return cmp.Compare(b.Bytes, a.Bytes)
 		}
-		return result[i].PID < result[j].PID
+		return cmp.Compare(a.PID, b.PID)
 	})
 	return result
 }
@@ -136,8 +137,14 @@ func (a *processAccumulator) compactIfNeeded() {
 	for _, stats := range a.byPID {
 		ordered = append(ordered, stats)
 	}
-	sort.Slice(ordered, func(i, j int) bool {
-		return betterProcessRank(ordered[i], ordered[j])
+	slices.SortFunc(ordered, func(a, b *processStats) int {
+		if betterProcessRank(a, b) {
+			return -1
+		}
+		if betterProcessRank(b, a) {
+			return 1
+		}
+		return 0
 	})
 	if len(ordered) > a.topN {
 		ordered = ordered[:a.topN]
diff --git a/internal/statsengine/syscall.go b/internal/statsengine/syscall.go
index 4feeab2..93931d1 100644
--- a/internal/statsengine/syscall.go
+++ b/internal/statsengine/syscall.go
@@ -1,9 +1,10 @@
 package statsengine
 
 import (
+	"cmp"
 	"math"
-	"math/rand"
-	"sort"
+	"math/rand/v2"
+	"slices"
 	"time"
 
 	"ior/internal/event"
@@ -55,15 +56,17 @@ type syscallSnapshotInput struct {
 }
 
 func newSyscallAccumulator() *syscallAccumulator {
-	return newSyscallAccumulatorWithConfig(syscallReservoirSampleCapDefault, rand.New(rand.NewSource(time.Now().UnixNano())))
+	return newSyscallAccumulatorWithConfig(syscallReservoirSampleCapDefault, nil)
 }
 
+// newSyscallAccumulatorWithConfig creates a syscall accumulator with the given
+// sample capacity and optional RNG. A nil rng uses the auto-seeded default.
 func newSyscallAccumulatorWithConfig(sampleCap int, rng *rand.Rand) *syscallAccumulator {
 	if sampleCap <= 0 {
 		sampleCap = syscallReservoirSampleCapDefault
 	}
 	if rng == nil {
-		rng = rand.New(rand.NewSource(time.Now().UnixNano()))
+		rng = rand.New(rand.NewPCG(rand.Uint64(), rand.Uint64()))
 	}
 
 	return &syscallAccumulator{
@@ -135,11 +138,11 @@ func buildSyscallSnapshots(inputs []syscallSnapshotInput, elapsed time.Duration)
 	for _, in := range inputs {
 		result = append(result, in.toSnapshot(rateDiv))
 	}
-	sort.Slice(result, func(i, j int) bool {
-		if result[i].Count != result[j].Count {
-			return result[i].Count > result[j].Count
+	slices.SortFunc(result, func(a, b SyscallSnapshot) int {
+		if a.Count != b.Count {
+			return cmp.Compare(b.Count, a.Count)
 		}
-		return result[i].Name < result[j].Name
+		return cmp.Compare(a.Name, b.Name)
 	})
 	return result
 }
@@ -161,8 +164,8 @@ func (s *syscallStats) addSample(duration uint64, cap int, rng *rand.Rand) {
 		return
 	}
 
-	idx := rng.Int63n(int64(s.seenLatencies))
-	if idx >= int64(cap) {
+	idx := rng.IntN(int(s.seenLatencies))
+	if idx >= cap {
 		return
 	}
 	s.samples[idx] = duration
@@ -183,7 +186,7 @@ func (s *syscallStats) ensurePercentiles() {
 	}
 
 	sorted := append([]uint64(nil), s.samples...)
-	sort.Slice(sorted, func(i, j int) bool { return sorted[i] < sorted[j] })
+	slices.Sort(sorted)
 	s.cachedP50 = samplePercentile(sorted, 0.50)
 	s.cachedP95 = samplePercentile(sorted, 0.95)
 	s.cachedP99 = samplePercentile(sorted, 0.99)
diff --git a/internal/statsengine/syscall_test.go b/internal/statsengine/syscall_test.go
index b315bd8..b00582d 100644
--- a/internal/statsengine/syscall_test.go
+++ b/internal/statsengine/syscall_test.go
@@ -2,7 +2,7 @@ package statsengine
 
 import (
 	"math"
-	"math/rand"
+	"math/rand/v2"
 	"testing"
 	"time"
 
@@ -11,7 +11,7 @@ import (
 )
 
 func TestSyscallAccumulatorBasicStats(t *testing.T) {
-	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewSource(1)))
+	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewPCG(1, 0)))
 	traceID := types.SYS_ENTER_READ
 
 	acc.Add(newPair(traceID, 10, 100, 0))
@@ -54,7 +54,7 @@ func TestSyscallAccumulatorBasicStats(t *testing.T) {
 }
 
 func TestSyscallAccumulatorSortsByCountThenName(t *testing.T) {
-	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewSource(2)))
+	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewPCG(2, 0)))
 
 	idA := types.SYS_ENTER_OPENAT
 	idB := types.SYS_ENTER_READ
@@ -76,7 +76,7 @@ func TestSyscallAccumulatorSortsByCountThenName(t *testing.T) {
 }
 
 func TestSyscallAccumulatorReservoirPercentilesAccuracy(t *testing.T) {
-	acc := newSyscallAccumulatorWithConfig(100, rand.New(rand.NewSource(7)))
+	acc := newSyscallAccumulatorWithConfig(100, rand.New(rand.NewPCG(7, 0)))
 	traceID := types.SYS_ENTER_WRITE
 
 	for d := uint64(1); d <= 10_000; d++ {
@@ -95,7 +95,7 @@ func TestSyscallAccumulatorReservoirPercentilesAccuracy(t *testing.T) {
 }
 
 func TestSyscallAccumulatorZeroElapsedRate(t *testing.T) {
-	acc := newSyscallAccumulatorWithConfig(32, rand.New(rand.NewSource(9)))
+	acc := newSyscallAccumulatorWithConfig(32, rand.New(rand.NewPCG(9, 0)))
 	acc.Add(newPair(types.SYS_ENTER_READ, 9, 0, 0))
 
 	snap := acc.Snapshot(0)
@@ -108,7 +108,7 @@ func TestSyscallAccumulatorZeroElapsedRate(t *testing.T) {
 }
 
 func TestSyscallAccumulatorPercentilesRecomputeAfterThreshold(t *testing.T) {
-	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewSource(11)))
+	acc := newSyscallAccumulatorWithConfig(10_000, rand.New(rand.NewPCG(11, 0)))
 	traceID := types.SYS_ENTER_READ
 
 	for i := 1; i <= 1000; i++ {