Re: [RFC PATCH 0/4] softirq: Per vector threading v3

David Miller
2018-01-24T15:06:03Z

From: Paolo Abeni <pabeni@redhat.com>
Date: Wed, 24 Jan 2018 15:54:05 +0100

> Niklas suggested a possible relation with CONFIG_IRQ_TIME_ACCOUNTING=y
> and indeed he was right.
>
> The patched kernel under test had CONFIG_IRQ_TIME_ACCOUNTING set, and
> very little CPU time was accounted to the kworker:
>
> [2125 is the relevant kworker's pid]
> grep sum_exec_runtime /proc/2125/sched; sleep 10; grep sum_exec_runtime /proc/2125/sched
> se.sum_exec_runtime : 13408.239286
> se.sum_exec_runtime : 13456.907197
>
> despite such process was processing a lot of packets and basically
> burning a CPU.

So IRQ_TIME_ACCOUNTING makes the scheduler think that the worker
threads are using nearly no task time at all.

The existing ksoftirqd code should hit the same problem, right?