Add staged NVIDIA burn ramp-up mode

2026-04-09 15:21:14 +03:00
parent a78fdadd88
commit 9481ca2805
11 changed files with 226 additions and 47 deletions
--- a/audit/internal/app/app.go
+++ b/audit/internal/app/app.go
@@ -117,7 +117,7 @@ type satRunner interface {
 	RunNvidiaAcceptancePackWithOptions(ctx context.Context, baseDir string, diagLevel int, gpuIndices []int, logFunc func(string)) (string, error)
 	RunNvidiaTargetedStressValidatePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error)
 	RunNvidiaBenchmark(ctx context.Context, baseDir string, opts platform.NvidiaBenchmarkOptions, logFunc func(string)) (string, error)
-	RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error)
+	RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, staggerSec int, logFunc func(string)) (string, error)
 	RunNvidiaTargetedPowerPack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error)
 	RunNvidiaPulseTestPack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error)
 	RunNvidiaBandwidthPack(ctx context.Context, baseDir string, gpuIndices []int, logFunc func(string)) (string, error)
@@ -566,11 +566,11 @@ func (a *App) RunNvidiaBenchmarkCtx(ctx context.Context, baseDir string, opts pl
 	return a.sat.RunNvidiaBenchmark(ctx, baseDir, opts, logFunc)
 }

-func (a *App) RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error) {
+func (a *App) RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, staggerSec int, logFunc func(string)) (string, error) {
 	if strings.TrimSpace(baseDir) == "" {
 		baseDir = DefaultSATBaseDir
 	}
-	return a.sat.RunNvidiaOfficialComputePack(ctx, baseDir, durationSec, gpuIndices, logFunc)
+	return a.sat.RunNvidiaOfficialComputePack(ctx, baseDir, durationSec, gpuIndices, staggerSec, logFunc)
 }

 func (a *App) RunNvidiaTargetedPowerPack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error) {
--- a/audit/internal/app/app_test.go
+++ b/audit/internal/app/app_test.go
@@ -161,7 +161,7 @@ func (f fakeSAT) RunNvidiaTargetedStressValidatePack(_ context.Context, baseDir
 	return f.runNvidiaFn(baseDir)
 }

-func (f fakeSAT) RunNvidiaOfficialComputePack(_ context.Context, baseDir string, durationSec int, gpuIndices []int, _ func(string)) (string, error) {
+func (f fakeSAT) RunNvidiaOfficialComputePack(_ context.Context, baseDir string, durationSec int, gpuIndices []int, _ int, _ func(string)) (string, error) {
 	if f.runNvidiaComputeFn != nil {
 		return f.runNvidiaComputeFn(baseDir, durationSec, gpuIndices)
 	}
--- a/audit/internal/platform/nvidia_stress.go
+++ b/audit/internal/platform/nvidia_stress.go
@@ -49,6 +49,9 @@ func buildNvidiaStressJob(opts NvidiaStressOptions) (satJob, error) {
 			"--seconds", strconv.Itoa(opts.DurationSec),
 			"--size-mb", strconv.Itoa(opts.SizeMB),
 		}
+		if opts.StaggerSeconds > 0 && len(selected) > 1 {
+			cmd = append(cmd, "--stagger-seconds", strconv.Itoa(opts.StaggerSeconds))
+		}
 		if len(selected) > 0 {
 			cmd = append(cmd, "--devices", joinIndexList(selected))
 		}
@@ -63,6 +66,9 @@ func buildNvidiaStressJob(opts NvidiaStressOptions) (satJob, error) {
 			"bee-john-gpu-stress",
 			"--seconds", strconv.Itoa(opts.DurationSec),
 		}
+		if opts.StaggerSeconds > 0 && len(selected) > 1 {
+			cmd = append(cmd, "--stagger-seconds", strconv.Itoa(opts.StaggerSeconds))
+		}
 		if len(selected) > 0 {
 			cmd = append(cmd, "--devices", joinIndexList(selected))
 		}
--- a/audit/internal/platform/sat.go
+++ b/audit/internal/platform/sat.go
@@ -384,25 +384,39 @@ func (s *System) RunNCCLTests(ctx context.Context, baseDir string, logFunc func(
 	), logFunc)
 }

-func (s *System) RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, logFunc func(string)) (string, error) {
+func (s *System) RunNvidiaOfficialComputePack(ctx context.Context, baseDir string, durationSec int, gpuIndices []int, staggerSec int, logFunc func(string)) (string, error) {
 	selected, err := resolveDCGMGPUIndices(gpuIndices)
 	if err != nil {
 		return "", err
 	}
-	profCmd, err := resolveDCGMProfTesterCommand("--no-dcgm-validation", "-t", "1004", "-d", strconv.Itoa(normalizeNvidiaBurnDuration(durationSec)))
-	if err != nil {
-		return "", err
+	var (
+		profCmd []string
+		profEnv []string
+	)
+	if staggerSec > 0 && len(selected) > 1 {
+		profCmd = []string{
+			"bee-dcgmproftester-staggered",
+			"--seconds", strconv.Itoa(normalizeNvidiaBurnDuration(durationSec)),
+			"--stagger-seconds", strconv.Itoa(staggerSec),
+			"--devices", joinIndexList(selected),
+		}
+	} else {
+		profCmd, err = resolveDCGMProfTesterCommand("--no-dcgm-validation", "-t", "1004", "-d", strconv.Itoa(normalizeNvidiaBurnDuration(durationSec)))
+		if err != nil {
+			return "", err
+		}
+		profEnv = nvidiaVisibleDevicesEnv(selected)
 	}
 	return runAcceptancePackCtx(ctx, baseDir, "gpu-nvidia-compute", withNvidiaPersistenceMode(
 		satJob{name: "01-nvidia-smi-q.log", cmd: []string{"nvidia-smi", "-q"}},
 		satJob{name: "02-dcgmi-version.log", cmd: []string{"dcgmi", "-v"}},
-		satJob{
-			name:       "03-dcgmproftester.log",
-			cmd:        profCmd,
-			env:        nvidiaVisibleDevicesEnv(selected),
-			collectGPU: true,
-			gpuIndices: selected,
-		},
+			satJob{
+				name:       "03-dcgmproftester.log",
+				cmd:        profCmd,
+				env:        profEnv,
+				collectGPU: true,
+				gpuIndices: selected,
+			},
 		satJob{name: "04-nvidia-smi-after.log", cmd: []string{"nvidia-smi", "--query-gpu=index,name,temperature.gpu,power.draw,utilization.gpu,memory.used,memory.total", "--format=csv,noheader,nounits"}},
 	), logFunc)
 }
--- a/audit/internal/platform/types.go
+++ b/audit/internal/platform/types.go
@@ -70,6 +70,7 @@ type NvidiaStressOptions struct {
 	Loader            string
 	GPUIndices        []int
 	ExcludeGPUIndices []int
+	StaggerSeconds    int
 }

 func New() *System {
--- a/audit/internal/webui/api.go
+++ b/audit/internal/webui/api.go
@@ -482,12 +482,13 @@ func (h *handler) handleAPISATRun(target string) http.HandlerFunc {
 			return
 		}

-		var body struct {
-			Duration           int      `json:"duration"`
-			StressMode         bool     `json:"stress_mode"`
-			GPUIndices         []int    `json:"gpu_indices"`
-			ExcludeGPUIndices  []int    `json:"exclude_gpu_indices"`
-			Loader             string   `json:"loader"`
+			var body struct {
+				Duration           int      `json:"duration"`
+				StressMode         bool     `json:"stress_mode"`
+				GPUIndices         []int    `json:"gpu_indices"`
+				ExcludeGPUIndices  []int    `json:"exclude_gpu_indices"`
+				StaggerGPUStart    bool     `json:"stagger_gpu_start"`
+				Loader             string   `json:"loader"`
 			Profile            string   `json:"profile"`
 			DisplayName        string   `json:"display_name"`
 			PlatformComponents []string `json:"platform_components"`
@@ -503,12 +504,13 @@ func (h *handler) handleAPISATRun(target string) http.HandlerFunc {
 		if strings.TrimSpace(body.DisplayName) != "" {
 			name = body.DisplayName
 		}
-		params := taskParams{
-			Duration:           body.Duration,
-			StressMode:         body.StressMode,
-			GPUIndices:         body.GPUIndices,
-			ExcludeGPUIndices:  body.ExcludeGPUIndices,
-			Loader:             body.Loader,
+			params := taskParams{
+				Duration:           body.Duration,
+				StressMode:         body.StressMode,
+				GPUIndices:         body.GPUIndices,
+				ExcludeGPUIndices:  body.ExcludeGPUIndices,
+				StaggerGPUStart:    body.StaggerGPUStart,
+				Loader:             body.Loader,
 			BurnProfile:        body.Profile,
 			DisplayName:        body.DisplayName,
 			PlatformComponents: body.PlatformComponents,
--- a/audit/internal/webui/pages.go
+++ b/audit/internal/webui/pages.go
@@ -2117,12 +2117,16 @@ func renderBurn() string {
      <button class="btn btn-sm btn-secondary" type="button" onclick="burnSelectAll()">Select All</button>
      <button class="btn btn-sm btn-secondary" type="button" onclick="burnSelectNone()">Clear</button>
    </div>
-    <div id="burn-gpu-list" style="border:1px solid var(--border);border-radius:4px;padding:12px;min-height:88px">
-      <p style="color:var(--muted);font-size:13px">Loading NVIDIA GPUs...</p>
-    </div>
-    <p id="burn-selection-note" style="font-size:12px;color:var(--muted);margin:10px 0 0">Select at least one NVIDIA GPU to enable NVIDIA burn recipes.</p>
-  </div>
-</div>
+	    <div id="burn-gpu-list" style="border:1px solid var(--border);border-radius:4px;padding:12px;min-height:88px">
+	      <p style="color:var(--muted);font-size:13px">Loading NVIDIA GPUs...</p>
+	    </div>
+	    <p id="burn-selection-note" style="font-size:12px;color:var(--muted);margin:10px 0 0">Select at least one NVIDIA GPU to enable NVIDIA burn recipes.</p>
+	    <label class="cb-row" style="margin-top:10px">
+	      <input type="checkbox" id="burn-stagger-nvidia">
+	      <span>Ramp selected NVIDIA GPUs one by one before full-load hold. Uses a 3-minute stabilization window per GPU, then keeps all selected GPUs under load for the chosen Burn Profile duration.</span>
+	    </label>
+	  </div>
+	</div>

 <div class="burn-section">Core Burn Paths</div>
 <div class="grid2 burn-grid" style="margin-bottom:16px">
@@ -2196,6 +2200,11 @@ function burnSelectedGPUIndices() {
    .sort(function(a, b) { return a - b; });
 }

+function burnUseNvidiaRampUp() {
+  const el = document.getElementById('burn-stagger-nvidia');
+  return !!(el && el.checked);
+}
+
 function burnUpdateSelectionNote() {
  const note = document.getElementById('burn-selection-note');
  const selected = burnSelectedGPUIndices();
@@ -2255,6 +2264,9 @@ function enqueueBurnTask(target, label, extra, useSelectedNvidia) {
      return Promise.reject(new Error('Select at least one NVIDIA GPU.'));
    }
    body.gpu_indices = selected;
+    if (burnUseNvidiaRampUp() && selected.length > 1) {
+      body.stagger_gpu_start = true;
+    }
  }
  return fetch('/api/sat/' + target + '/run', {
    method: 'POST',
--- a/audit/internal/webui/tasks.go
+++ b/audit/internal/webui/tasks.go
@@ -118,6 +118,7 @@ type taskParams struct {
 	StressMode         bool     `json:"stress_mode,omitempty"`
 	GPUIndices         []int    `json:"gpu_indices,omitempty"`
 	ExcludeGPUIndices  []int    `json:"exclude_gpu_indices,omitempty"`
+	StaggerGPUStart    bool     `json:"stagger_gpu_start,omitempty"`
 	SizeMB             int      `json:"size_mb,omitempty"`
 	Passes             int      `json:"passes,omitempty"`
 	Loader             string   `json:"loader,omitempty"`
@@ -162,6 +163,13 @@ func resolveBurnPreset(profile string) burnPreset {
 	}
 }

+func boolToNvidiaStaggerSeconds(enabled bool, selected []int) int {
+	if enabled && len(selected) > 1 {
+		return 180
+	}
+	return 0
+}
+
 func resolvePlatformStressPreset(profile string) platform.PlatformStressOptions {
 	acceptanceCycles := []platform.PlatformStressCycle{
 		{LoadSec: 85, IdleSec: 5},
@@ -592,7 +600,7 @@ func (q *taskQueue) runTask(t *Task, j *jobState, ctx context.Context) {
 			RunNCCL:           t.params.RunNCCL,
 			ParallelGPUs:      t.params.ParallelGPUs,
 		}, j.append)
-	case "nvidia-compute":
+		case "nvidia-compute":
 		if a == nil {
 			err = fmt.Errorf("app not configured")
 			break
@@ -601,7 +609,11 @@ func (q *taskQueue) runTask(t *Task, j *jobState, ctx context.Context) {
 		if t.params.BurnProfile != "" && dur <= 0 {
 			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
 		}
-		archive, err = a.RunNvidiaOfficialComputePack(ctx, "", dur, t.params.GPUIndices, j.append)
+			staggerSec := boolToNvidiaStaggerSeconds(t.params.StaggerGPUStart, t.params.GPUIndices)
+			if staggerSec > 0 {
+				j.append(fmt.Sprintf("NVIDIA staggered ramp-up enabled: %ds per GPU", staggerSec))
+			}
+			archive, err = a.RunNvidiaOfficialComputePack(ctx, "", dur, t.params.GPUIndices, staggerSec, j.append)
 	case "nvidia-targeted-power":
 		if a == nil {
 			err = fmt.Errorf("app not configured")
@@ -651,12 +663,13 @@ func (q *taskQueue) runTask(t *Task, j *jobState, ctx context.Context) {
 		if t.params.BurnProfile != "" && dur <= 0 {
 			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
 		}
-		archive, err = runNvidiaStressPackCtx(a, ctx, "", platform.NvidiaStressOptions{
-			DurationSec:       dur,
-			Loader:            t.params.Loader,
-			GPUIndices:        t.params.GPUIndices,
-			ExcludeGPUIndices: t.params.ExcludeGPUIndices,
-		}, j.append)
+			archive, err = runNvidiaStressPackCtx(a, ctx, "", platform.NvidiaStressOptions{
+				DurationSec:       dur,
+				Loader:            t.params.Loader,
+				GPUIndices:        t.params.GPUIndices,
+				ExcludeGPUIndices: t.params.ExcludeGPUIndices,
+				StaggerSeconds:    boolToNvidiaStaggerSeconds(t.params.StaggerGPUStart, t.params.GPUIndices),
+			}, j.append)
 	case "memory":
 		if a == nil {
 			err = fmt.Errorf("app not configured")
--- a/iso/overlay/usr/local/bin/bee-dcgmproftester-staggered
+++ b/iso/overlay/usr/local/bin/bee-dcgmproftester-staggered
@@ -0,0 +1,110 @@
+#!/bin/sh
+set -eu
+
+SECONDS=300
+STAGGER_SECONDS=180
+DEVICES=""
+EXCLUDE=""
+
+usage() {
+    echo "usage: $0 [--seconds N] [--stagger-seconds N] [--devices 0,1] [--exclude 2,3]" >&2
+    exit 2
+}
+
+normalize_list() {
+    echo "${1:-}" | tr ',' '\n' | sed 's/[[:space:]]//g' | awk 'NF' | sort -n | uniq | paste -sd, -
+}
+
+contains_csv() {
+    needle="$1"
+    haystack="${2:-}"
+    echo ",${haystack}," | grep -q ",${needle},"
+}
+
+resolve_dcgmproftester() {
+    for candidate in dcgmproftester dcgmproftester13 dcgmproftester12 dcgmproftester11; do
+        if command -v "${candidate}" >/dev/null 2>&1; then
+            command -v "${candidate}"
+            return 0
+        fi
+    done
+    return 1
+}
+
+while [ "$#" -gt 0 ]; do
+    case "$1" in
+        --seconds|-t) [ "$#" -ge 2 ] || usage; SECONDS="$2"; shift 2 ;;
+        --stagger-seconds) [ "$#" -ge 2 ] || usage; STAGGER_SECONDS="$2"; shift 2 ;;
+        --devices) [ "$#" -ge 2 ] || usage; DEVICES="$2"; shift 2 ;;
+        --exclude) [ "$#" -ge 2 ] || usage; EXCLUDE="$2"; shift 2 ;;
+        *) usage ;;
+    esac
+done
+
+PROF=$(resolve_dcgmproftester) || { echo "dcgmproftester not found in PATH" >&2; exit 1; }
+ALL_DEVICES=$(nvidia-smi --query-gpu=index --format=csv,noheader,nounits 2>/dev/null | sed 's/[[:space:]]//g' | awk 'NF' | paste -sd, -)
+[ -n "${ALL_DEVICES}" ] || { echo "nvidia-smi found no NVIDIA GPUs" >&2; exit 1; }
+
+DEVICES=$(normalize_list "${DEVICES}")
+EXCLUDE=$(normalize_list "${EXCLUDE}")
+SELECTED="${DEVICES}"
+if [ -z "${SELECTED}" ]; then
+    SELECTED="${ALL_DEVICES}"
+fi
+
+FINAL=""
+for id in $(echo "${SELECTED}" | tr ',' ' '); do
+    [ -n "${id}" ] || continue
+    if contains_csv "${id}" "${EXCLUDE}"; then
+        continue
+    fi
+    if [ -z "${FINAL}" ]; then
+        FINAL="${id}"
+    else
+        FINAL="${FINAL},${id}"
+    fi
+done
+
+[ -n "${FINAL}" ] || { echo "no NVIDIA GPUs selected after filters" >&2; exit 1; }
+
+echo "loader=dcgmproftester-staggered"
+echo "selected_gpus=${FINAL}"
+echo "stagger_seconds=${STAGGER_SECONDS}"
+
+TMP_DIR=$(mktemp -d)
+trap 'rm -rf "${TMP_DIR}"' EXIT INT TERM
+
+GPU_COUNT=$(echo "${FINAL}" | tr ',' '\n' | awk 'NF' | wc -l | tr -d '[:space:]')
+gpu_pos=0
+WORKERS=""
+for id in $(echo "${FINAL}" | tr ',' ' '); do
+    gpu_pos=$((gpu_pos + 1))
+    log="${TMP_DIR}/gpu-${id}.log"
+    extra_sec=$(( STAGGER_SECONDS * (GPU_COUNT - gpu_pos) ))
+    gpu_seconds=$(( SECONDS + extra_sec ))
+    echo "starting gpu ${id} seconds=${gpu_seconds}"
+    CUDA_VISIBLE_DEVICES="${id}" "${PROF}" --no-dcgm-validation -t 1004 -d "${gpu_seconds}" >"${log}" 2>&1 &
+    pid=$!
+    WORKERS="${WORKERS} ${pid}:${id}:${log}"
+    if [ "${STAGGER_SECONDS}" -gt 0 ] && [ "${gpu_pos}" -lt "${GPU_COUNT}" ]; then
+        sleep "${STAGGER_SECONDS}"
+    fi
+done
+
+status=0
+for spec in ${WORKERS}; do
+    pid=${spec%%:*}
+    rest=${spec#*:}
+    id=${rest%%:*}
+    log=${rest#*:}
+    if wait "${pid}"; then
+        echo "gpu ${id} finished: OK"
+    else
+        rc=$?
+        echo "gpu ${id} finished: FAILED rc=${rc}"
+        status=1
+    fi
+    sed "s/^/[gpu ${id}] /" "${log}" || true
+done
+
+exit "${status}"
--- a/iso/overlay/usr/local/bin/bee-gpu-burn
+++ b/iso/overlay/usr/local/bin/bee-gpu-burn
@@ -2,13 +2,14 @@
 set -eu

 SECONDS=5
+STAGGER_SECONDS=0
 SIZE_MB=0
 DEVICES=""
 EXCLUDE=""
 WORKER="/usr/local/lib/bee/bee-gpu-burn-worker"

 usage() {
-    echo "usage: $0 [--seconds N] [--size-mb N] [--devices 0,1] [--exclude 2,3]" >&2
+    echo "usage: $0 [--seconds N] [--stagger-seconds N] [--size-mb N] [--devices 0,1] [--exclude 2,3]" >&2
    exit 2
 }

@@ -25,6 +26,7 @@ contains_csv() {
 while [ "$#" -gt 0 ]; do
    case "$1" in
        --seconds|-t) [ "$#" -ge 2 ] || usage; SECONDS="$2"; shift 2 ;;
+        --stagger-seconds) [ "$#" -ge 2 ] || usage; STAGGER_SECONDS="$2"; shift 2 ;;
        --size-mb|-m) [ "$#" -ge 2 ] || usage; SIZE_MB="$2"; shift 2 ;;
        --devices) [ "$#" -ge 2 ] || usage; DEVICES="$2"; shift 2 ;;
        --exclude) [ "$#" -ge 2 ] || usage; EXCLUDE="$2"; shift 2 ;;
@@ -61,14 +63,18 @@ done

 echo "loader=bee-gpu-burn"
 echo "selected_gpus=${FINAL}"
+echo "stagger_seconds=${STAGGER_SECONDS}"

 export CUDA_DEVICE_ORDER="PCI_BUS_ID"

 TMP_DIR=$(mktemp -d)
 trap 'rm -rf "${TMP_DIR}"' EXIT INT TERM

+GPU_COUNT=$(echo "${FINAL}" | tr ',' '\n' | awk 'NF' | wc -l | tr -d '[:space:]')
+gpu_pos=0
 WORKERS=""
 for id in $(echo "${FINAL}" | tr ',' ' '); do
+    gpu_pos=$((gpu_pos + 1))
    log="${TMP_DIR}/gpu-${id}.log"
    gpu_size_mb="${SIZE_MB}"
    if [ "${gpu_size_mb}" -le 0 ] 2>/dev/null; then
@@ -79,11 +85,16 @@ for id in $(echo "${FINAL}" | tr ',' ' '); do
            gpu_size_mb=512
        fi
    fi
-    echo "starting gpu ${id} size=${gpu_size_mb}MB"
+    extra_sec=$(( STAGGER_SECONDS * (GPU_COUNT - gpu_pos) ))
+    gpu_seconds=$(( SECONDS + extra_sec ))
+    echo "starting gpu ${id} size=${gpu_size_mb}MB seconds=${gpu_seconds}"
    CUDA_VISIBLE_DEVICES="${id}" \
-        "${WORKER}" --device 0 --seconds "${SECONDS}" --size-mb "${gpu_size_mb}" >"${log}" 2>&1 &
+        "${WORKER}" --device 0 --seconds "${gpu_seconds}" --size-mb "${gpu_size_mb}" >"${log}" 2>&1 &
    pid=$!
    WORKERS="${WORKERS} ${pid}:${id}:${log}"
+    if [ "${STAGGER_SECONDS}" -gt 0 ] && [ "${gpu_pos}" -lt "${GPU_COUNT}" ]; then
+        sleep "${STAGGER_SECONDS}"
+    fi
 done

 status=0
--- a/iso/overlay/usr/local/bin/bee-john-gpu-stress
+++ b/iso/overlay/usr/local/bin/bee-john-gpu-stress
@@ -2,6 +2,7 @@
 set -eu

 DURATION_SEC=300
+STAGGER_SECONDS=0
 DEVICES=""
 EXCLUDE=""
 FORMAT=""
@@ -12,7 +13,7 @@ export OCL_ICD_VENDORS="/etc/OpenCL/vendors"
 export LD_LIBRARY_PATH="/usr/lib:/usr/local/lib${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}"

 usage() {
-    echo "usage: $0 [--seconds N] [--devices 0,1] [--exclude 2,3] [--format name]" >&2
+    echo "usage: $0 [--seconds N] [--stagger-seconds N] [--devices 0,1] [--exclude 2,3] [--format name]" >&2
    exit 2
 }

@@ -118,6 +119,7 @@ ensure_opencl_ready() {
 while [ "$#" -gt 0 ]; do
    case "$1" in
        --seconds|-t) [ "$#" -ge 2 ] || usage; DURATION_SEC="$2"; shift 2 ;;
+        --stagger-seconds) [ "$#" -ge 2 ] || usage; STAGGER_SECONDS="$2"; shift 2 ;;
        --devices) [ "$#" -ge 2 ] || usage; DEVICES="$2"; shift 2 ;;
        --exclude) [ "$#" -ge 2 ] || usage; EXCLUDE="$2"; shift 2 ;;
        --format) [ "$#" -ge 2 ] || usage; FORMAT="$2"; shift 2 ;;
@@ -170,6 +172,7 @@ done
 echo "loader=john"
 echo "selected_gpus=${FINAL}"
 echo "john_devices=${JOHN_DEVICES}"
+echo "stagger_seconds=${STAGGER_SECONDS}"

 cd "${JOHN_DIR}"

@@ -232,14 +235,21 @@ trap cleanup EXIT INT TERM
 echo "format=${CHOSEN_FORMAT}"
 echo "target_seconds=${DURATION_SEC}"
 echo "slice_seconds=${TEST_SLICE_SECONDS}"
-DEADLINE=$(( $(date +%s) + DURATION_SEC ))
+TOTAL_DEVICES=$(echo "${JOHN_DEVICES}" | tr ',' '\n' | awk 'NF' | wc -l | tr -d '[:space:]')
 _first=1
+pos=0
 for opencl_id in $(echo "${JOHN_DEVICES}" | tr ',' ' '); do
+    pos=$((pos + 1))
    [ "${_first}" = "1" ] || sleep 3
    _first=0
-    run_john_loop "${opencl_id}" "${DEADLINE}" &
+    extra_sec=$(( STAGGER_SECONDS * (TOTAL_DEVICES - pos) ))
+    deadline=$(( $(date +%s) + DURATION_SEC + extra_sec ))
+    run_john_loop "${opencl_id}" "${deadline}" &
    pid=$!
    PIDS="${PIDS} ${pid}"
+    if [ "${STAGGER_SECONDS}" -gt 0 ] && [ "${pos}" -lt "${TOTAL_DEVICES}" ]; then
+        sleep "${STAGGER_SECONDS}"
+    fi
 done
 FAIL=0
 for pid in ${PIDS}; do