Re: [RFC PATCH v8 3/4] blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary

[Tejun Heo <tj@kernel.org>]

Hello, Tao.

The following is a Claude-generated review.

On Wed, 30 Sep 2026 15:51:53 +0800, Tao Cui wrote:
> Add iocost_ioc_tick, emitted once per period from the tail of
> ioc_timer_fn() with the overall controller state: period_us, vrate,
> busy_level, active iocg count, usage percentage and running state.
> It fires every period the controller is running, including steady
> states, plus one final tick before the controller goes idle, which
> makes dormancy (e.g. a device saturated entirely by uncharged IO)
> directly visible.
...
> +		__entry->running = ioc->running;

The timer only runs while ioc->running is IOC_RUNNING and the switch to
IOC_IDLE happens after the trace call, so this field always reads running
except when racing ioc_rqos_exit(). The final tick before going idle
reads active=0 running=1, and dormancy is only visible through the ticks
stopping, not through the field. Can you either drop the field or report
list_empty(&ioc->active_iocgs), and adjust the description? The event is
also emitted before the vrate adjustment and the period transition, not
from the tail of the function.

Thanks.

--
tejun