3 files changed, 51 insertions, 1 deletions
diff --git a/internal/flags/flags.go b/internal/flags/flags.go
index 547ba8e..cc39638 100644
--- a/internal/flags/flags.go
+++ b/internal/flags/flags.go
@@ -265,7 +265,7 @@ func resolveSamplingRates(cfg *Config, familySampling, syscallSampling *string)
 		return err
 	}
 	cfg.SyscallFamilySamplingRates = familyRates
-	cfg.SyscallSamplingRates = syscallRates
+	cfg.SyscallSamplingRates = mergeSyscallSamplingRates(syscallRates)
 	return nil
 }
 
diff --git a/internal/flags/sampling.go b/internal/flags/sampling.go
index 19b4f9d..2f63ada 100644
--- a/internal/flags/sampling.go
+++ b/internal/flags/sampling.go
@@ -8,6 +8,14 @@ import (
 	"ior/internal/types"
 )
 
+var defaultAggregateOnlySyscalls = []string{
+	"futex",
+	"futex_wait",
+	"futex_wake",
+	"futex_requeue",
+	"futex_waitv",
+}
+
 func cloneFamilySamplingRates(in map[types.SyscallFamily]uint32) map[types.SyscallFamily]uint32 {
 	out := make(map[types.SyscallFamily]uint32, len(in))
 	for family, rate := range in {
@@ -24,6 +32,22 @@ func cloneSyscallSamplingRates(in map[string]uint32) map[string]uint32 {
 	return out
 }
 
+func defaultSyscallSamplingRates() map[string]uint32 {
+	out := make(map[string]uint32, len(defaultAggregateOnlySyscalls))
+	for _, syscall := range defaultAggregateOnlySyscalls {
+		out[syscall] = 0
+	}
+	return out
+}
+
+func mergeSyscallSamplingRates(overrides map[string]uint32) map[string]uint32 {
+	out := defaultSyscallSamplingRates()
+	for syscall, rate := range overrides {
+		out[syscall] = rate
+	}
+	return out
+}
+
 func parseFamilySamplingRates(raw string) (map[types.SyscallFamily]uint32, error) {
 	entries, err := parseSamplingEntries(raw)
 	if err != nil {
diff --git a/internal/flags/sampling_test.go b/internal/flags/sampling_test.go
index 0966c0f..82a43ec 100644
--- a/internal/flags/sampling_test.go
+++ b/internal/flags/sampling_test.go
@@ -76,3 +76,29 @@ func TestCloneDeepCopiesSamplingMaps(t *testing.T) {
 		t.Fatalf("original syscall rate mutated: got %d, want 9", got)
 	}
 }
+
+func TestDefaultSamplingRatesIncludeFutexAggregateOnly(t *testing.T) {
+	cfg, err := parseForTest(t)
+	if err != nil {
+		t.Fatalf("parse returned error: %v", err)
+	}
+	for _, syscall := range []string{"futex", "futex_wait", "futex_wake", "futex_requeue", "futex_waitv"} {
+		rate, ok := cfg.SyscallSamplingRates[syscall]
+		if !ok {
+			t.Fatalf("expected default sampling entry for %s", syscall)
+		}
+		if rate != 0 {
+			t.Fatalf("%s default rate = %d, want 0 (aggregate-only)", syscall, rate)
+		}
+	}
+}
+
+func TestParseSamplingRatesOverrideDefaultFutexRate(t *testing.T) {
+	cfg, err := parseForTest(t, "-syscall-sampling-syscalls", "futex=7")
+	if err != nil {
+		t.Fatalf("parse returned error: %v", err)
+	}
+	if got := cfg.SyscallSamplingRates["futex"]; got != 7 {
+		t.Fatalf("futex rate = %d, want 7", got)
+	}
+}