Impact: jiffies increment too fast. Hugh Dickins noted that with NOHZ=n and HIGHRES=n jiffies get incremented too fast. The reason is a wrong check in the broadcast enter/exit code, which keeps the local apic timer in periodic mode when the switch happens.
Showing the changes to kernel (1 of 1 file). Show all
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| @@ -235,7 +235,8 @@ static void tick_do_broadcast_on_off(void *why) · 234 unmodified lines | |||
| 235 | case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: | 235 | case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: |
| 236 | if (!cpu_isset(cpu, tick_broadcast_mask)) { | 236 | if (!cpu_isset(cpu, tick_broadcast_mask)) { |
| 237 | cpu_set(cpu, tick_broadcast_mask); | 237 | cpu_set(cpu, tick_broadcast_mask); |
| 238 | if (bc->mode == TICKDEV_MODE_PERIODIC) | 238 | if (tick_broadcast_device.mode == |
| 239 | TICKDEV_MODE_PERIODIC) | ||
| 239 | clockevents_shutdown(dev); | 240 | clockevents_shutdown(dev); |
| 240 | } | 241 | } |
| 241 | if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE) | 242 | if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE) |
| @@ -245,7 +246,8 @@ static void tick_do_broadcast_on_off(void *why) · 3 unmodified lines | |||
| 245 | if (!tick_broadcast_force && | 246 | if (!tick_broadcast_force && |
| 246 | cpu_isset(cpu, tick_broadcast_mask)) { | 247 | cpu_isset(cpu, tick_broadcast_mask)) { |
| 247 | cpu_clear(cpu, tick_broadcast_mask); | 248 | cpu_clear(cpu, tick_broadcast_mask); |
| 248 | if (bc->mode == TICKDEV_MODE_PERIODIC) | 249 | if (tick_broadcast_device.mode == |
| 250 | TICKDEV_MODE_PERIODIC) | ||
| 249 | tick_setup_periodic(dev, 0); | 251 | tick_setup_periodic(dev, 0); |
| 250 | } | 252 | } |
| 251 | break; | 253 | break; |