From: Tejun Heo <tj@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Tao Cui <cui.tao@linux.dev>
Cc: josef@toxicopanda.com, axboe@kernel.dk, cgroups@vger.kernel.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, andrii@kernel.org, eddyz87@gmail.com,
daniel@iogearbox.net, linux-kselftest@vger.kernel.org,
cuitao@kylinos.cn, ameryhung@gmail.com
Subject: Re: [RFC PATCH v11 0/5] blk-iocost: BPF struct_ops cost model
Date: Wed, 28 Oct 2026 10:09:24 -1000 [thread overview]
Message-ID: <046eabc08a80c27d17581a3ff591c70b@kernel.org> (raw)
In-Reply-To: <DMGLGKYOLXFA.12EJEMVN58Y5P@gmail.com>
Hello, Alexei.
On Wed, Oct 28, 2026 at 03:58:57PM +0000, Alexei Starovoitov wrote:
> Lets drop them. A struct_ops can get new members later, when a model
> needs them.
> I'd like to hear from Tejun whether such a model is planned.
The callbacks would only be worth having if they could do something
calc_cost() can't, e.g. sleep, but I forgot that pd allocations are
opportunistic to begin with. A blkg and its pds are created on the bio
path under queue_lock with GFP_NOWAIT, so iocg_init() can't sleep
either. Agreed, let's drop them.
> ...
> calc_cost() runs under rcu_read_lock(). bpf_map_put() frees a struct_ops
> map after an RCU gp. So detach doesn't need to freeze the queue.
> The rest fits into blk-iocost.c and patch 1 is not needed.
Agreed on both.
Thanks.
--
tejun
next prev parent reply other threads:[~2026-10-28 20:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-28 14:35 [RFC PATCH v11 0/5] blk-iocost: BPF struct_ops cost model Tao Cui
2026-10-28 14:35 ` [PATCH 1/5] blk-iocost: move shared definitions to blk-iocost.h Tao Cui
2026-10-28 20:09 ` Tejun Heo
2026-10-28 14:35 ` [PATCH 2/5] blk-iocost: add BPF struct_ops cost model support Tao Cui
2026-10-28 15:33 ` bot+bpf-ci
2026-10-28 20:09 ` Tejun Heo
2026-10-28 14:35 ` [PATCH 3/5] selftests/bpf: add iocost cost model test Tao Cui
2026-10-28 15:33 ` bot+bpf-ci
2026-10-28 20:09 ` Tejun Heo
2026-10-28 14:35 ` [PATCH 4/5] blk-iocost: add iocost_ioc_tick tracepoint for per-period device summary Tao Cui
2026-10-28 20:09 ` Tejun Heo
2026-10-28 14:35 ` [PATCH 5/5] docs: cgroup-v2: document the iocost BPF cost model attachment Tao Cui
2026-10-28 20:09 ` Tejun Heo
2026-10-28 15:58 ` [RFC PATCH v11 0/5] blk-iocost: BPF struct_ops cost model Alexei Starovoitov
2026-10-28 20:09 ` Tejun Heo [this message]
2026-10-28 20:09 ` Tejun Heo
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