Re: [PATCH 4/5] blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary

[Tejun Heo]

Hello, Tao.

On Wed, Oct 28, 2026 at 10:35:33PM +0800, Tao Cui wrote:
>  		u64 vdone, vtime, usage_us;
>  		u32 hw_active, hw_inuse;
>
> +		nr_active++;

nr_active is counted even when the tracepoint is disabled.

> +	/*
> +	 * Everything the tick reports is final here: busy_level was just
> +	 * computed, cur_period hasn't changed, nr_active and usage_us_sum are
> +	 * complete, and vrate and period_us still hold the values this period
> +	 * ran in. usage is wall time over wall time, summed over iocgs, and is

An io.cost.qos write in the middle of a period changes both period_us
and vrate.

Thanks.

--
tejun