From: bot+bpf-ci@kernel.org
To: cui.tao@linux.dev,tj@kernel.org,josef@toxicopanda.com,axboe@kernel.dk,alexei.starovoitov@gmail.com
Cc: cgroups@vger.kernel.org,linux-block@vger.kernel.org,linux-kernel@vger.kernel.org,bpf@vger.kernel.org,andrii@kernel.org,eddyz87@gmail.com,ast@kernel.org,daniel@iogearbox.net,linux-kselftest@vger.kernel.org,cui.tao@linux.dev,cuitao@kylinos.cn,ameryhung@gmail.com,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev
Subject: Re: [RFC PATCH v13 2/4] blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary
Date: Fri, 6 Nov 2026 12:56:51 +0000 (UTC) [thread overview]
Message-ID: <ebb6ebc5ddce3089fe912ca2d6e7a0658864c7369d15e1cdb7f203eae6d5a0d0@mail.kernel.org> (raw)
In-Reply-To: <20261106122356.3224638-3-cui.tao@linux.dev>
[-- Attachment #1: Type: text/plain, Size: 1990 bytes --]
> blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary
TL;DR: Commit message only: it restates the code comment instead of giving the
motivation (monitoring without drgn) for the new iocost_ioc_tick tracepoint.
Not a bug.
> blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary
>
> Add iocost_ioc_tick, emitted once per period from ioc_timer_fn() with
> the overall controller state: period_us, vrate, busy_level, active iocg
> count and usage percentage. busy_level, cur_period, nr_active and
> usage_us_sum are complete at the emission point. usage is wall time
> over wall time, summed over iocgs, and is not capped at 100. vrate and
> period_us reflect the current controller state, which an io.cost.qos
> write may have changed mid-period.
>
> The event fires every period the controller is running, including
> steady states, plus one final tick before the controller goes idle, so
> the transition to dormancy is directly visible. The active iocg count
> is only gathered when the tracepoint is enabled.
>
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Tao Cui <cuitao@kylinos.cn>
this isn't a bug, but the middle of the first paragraph ("busy_level,
cur_period, nr_active and usage_us_sum are complete at the emission point
... which an io.cost.qos write may have changed mid-period") restates the
block comment added above the tracepoint call in ioc_timer_fn() almost word
for word.
The reason for adding the event only appears in the comment in
include/trace/events/iocost.h ("so basic monitoring doesn't require drgn").
Could the changelog say why a per-period summary event is needed, for
example the monitoring-without-drgn motivation, rather than repeating the
code comment?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/42219005018
next prev parent reply other threads:[~2026-11-06 12:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-06 12:23 [RFC PATCH v13 0/4] blk-iocost: BPF struct_ops cost model Tao Cui
2026-11-06 12:23 ` [RFC PATCH v13 1/4] blk-iocost: add BPF struct_ops cost model support Tao Cui
2026-11-06 12:23 ` [RFC PATCH v13 2/4] blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary Tao Cui
2026-11-06 12:56 ` bot+bpf-ci [this message]
2026-11-06 12:23 ` [RFC PATCH v13 3/4] selftests/bpf: add iocost cost model test Tao Cui
2026-11-06 12:56 ` bot+bpf-ci
2026-11-06 12:23 ` [RFC PATCH v13 4/4] docs: cgroup-v2: document the iocost BPF cost model attachment Tao Cui
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