pkg/cmd/roachtests: fix disk bandwidth passed to cluster setting

As of #135019, the disk bandwidth variable has units of bytes, but the
string passed to the cluster setting has units of `MiB`. This can result
an effective bandwidth that is orders of magnitude too high.

Change the former to match the units of the latter.

Release note: None.

Author: nicktrav

pkg/cmd/roachtest/tests/admission_control_disk_bandwidth_overload.go

@@ -72,7 +72,7 @@ func registerDiskBandwidthOverload(r registry.Registry) {
 			staller := roachtestutil.MakeCgroupDiskStaller(t, c,
 				false /* readsToo */, false /* logsToo */)
 			staller.Setup(ctx)
-			staller.Slow(ctx, c.CRDBNodes(), provisionedBandwidth)
+			staller.Slow(ctx, c.CRDBNodes(), provisionedBandwidth /* bytesPerSecond */)
 
 			// TODO(aaditya): Extend this test to also limit reads once we have a
 			// mechanism to pace read traffic in AC.
@@ -133,11 +133,11 @@ func registerDiskBandwidthOverload(r registry.Registry) {
 			db := c.Conn(ctx, t.L(), len(c.CRDBNodes()))
 			defer db.Close()
 
-			const bandwidthLimit = 75
+			const bandwidthLimitMbs = 75
 			if _, err := db.ExecContext(
 				// We intentionally set this to much lower than the provisioned value
 				// above to clearly show that the bandwidth limiter works.
-				ctx, fmt.Sprintf("SET CLUSTER SETTING kvadmission.store.provisioned_bandwidth = '%dMiB'", bandwidthLimit)); err != nil {
+				ctx, fmt.Sprintf("SET CLUSTER SETTING kvadmission.store.provisioned_bandwidth = '%dMiB'", bandwidthLimitMbs)); err != nil {
 				t.Fatalf("failed to set kvadmission.store.provisioned_bandwidth: %v", err)
 			}
 
@@ -170,7 +170,7 @@ func registerDiskBandwidthOverload(r registry.Registry) {
 				}
 
 				// Allow a 5% room for error.
-				const bandwidthThreshold = bandwidthLimit * 1.05
+				const bandwidthThreshold = bandwidthLimitMbs * 1.05
 				const sampleCountForBW = 12
 				const collectionIntervalSeconds = 10.0
 				// Loop for ~20 minutes.

pkg/cmd/roachtest/tests/admission_control_snapshot_overload_io.go

@@ -172,15 +172,15 @@ func runAdmissionControlSnapshotOverloadIO(
 
 	// Now set disk bandwidth limits
 	if cfg.limitDiskBandwidth {
-		const bandwidthLimit = 128 << 20 // 128 MiB
-		t.Status(fmt.Sprintf("limiting disk bandwidth to %d bytes/s", bandwidthLimit))
+		const bandwidthLimitMbs = 128
+		t.Status(fmt.Sprintf("limiting disk bandwidth to %d MB/s", bandwidthLimitMbs))
 		staller := roachtestutil.MakeCgroupDiskStaller(t, c,
 			false /* readsToo */, false /* logsToo */)
 		staller.Setup(ctx)
-		staller.Slow(ctx, c.CRDBNodes(), bandwidthLimit)
+		staller.Slow(ctx, c.CRDBNodes(), bandwidthLimitMbs<<20 /* bytesPerSecond */)
 
 		if _, err := db.ExecContext(
-			ctx, fmt.Sprintf("SET CLUSTER SETTING kvadmission.store.provisioned_bandwidth = '%dMiB'", bandwidthLimit)); err != nil {
+			ctx, fmt.Sprintf("SET CLUSTER SETTING kvadmission.store.provisioned_bandwidth = '%dMiB'", bandwidthLimitMbs)); err != nil {
 			t.Fatalf("failed to set kvadmission.store.provisioned_bandwidth: %v", err)
 		}
 		if _, err := db.ExecContext(