Add staged NVIDIA burn ramp-up mode

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