When __queue_delayed_work() is called, it chooses a cpu for handling the timer interrupt. As of today, it will pick either the cpu passed as parameter or the last cpu used for this. This is not good if a system does use CPU isolation, because it can take away some valuable cpu time to: 1 - deal with the timer interrupt, 2 - schedule-out the desired task, 3 - queue work on a random workqueue, and 4 - schedule the desired task back to the cpu. So to fix this, during __queue_delayed_work(), if cpu isolation is in place, pick a random non-isolated cpu to handle the timer interrupt. As an optimization, if the current cpu is not isolated, use it instead of looking for another candidate.
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| @@ -2362,10 +2362,18 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, · 2361 unmodified lines | |||
| 2362 | dwork->cpu = cpu; | 2362 | dwork->cpu = cpu; |
| 2363 | timer->expires = jiffies + delay; | 2363 | timer->expires = jiffies + delay; |
| 2364 | 2364 | ||
| 2365 | if (unlikely(cpu != WORK_CPU_UNBOUND)) | 2365 | if (housekeeping_enabled(HK_TYPE_TIMER)) { |
| 2366 | /* If the current cpu is a housekeeping cpu, use it. */ | ||
| 2367 | cpu = smp_processor_id(); | ||
| 2368 | if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER)) | ||
| 2369 | cpu = housekeeping_any_cpu(HK_TYPE_TIMER); | ||
| 2366 | add_timer_on(timer, cpu); | 2370 | add_timer_on(timer, cpu); |
| 2367 | else | 2371 | } else { |
| 2368 | add_timer(timer); | 2372 | if (likely(cpu == WORK_CPU_UNBOUND)) |
| 2373 | add_timer(timer); | ||
| 2374 | else | ||
| 2375 | add_timer_on(timer, cpu); | ||
| 2376 | } | ||
| 2369 | } | 2377 | } |
| 2370 | 2378 | ||
| 2371 | /** | 2379 | /** |