From: Christoph Hellwig <hch@infradead.org>
To: Tao Cui <cui.tao@linux.dev>
Cc: tj@kernel.org, josef@toxicopanda.com, axboe@kernel.dk,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, Tao Cui <cuitao@kylinos.cn>
Subject: Re: [PATCH 3/4] blk-iocost: account zone append completions in latency stats
Date: Wed, 9 Sep 2026 22:39:09 -0700 [thread overview]
Message-ID: <aqJCfZ8CNf1tVhM1@infradead.org> (raw)
In-Reply-To: <20260908022135.1429281-4-cui.tao@linux.dev>
On Tue, Sep 08, 2026 at 10:21:34AM +0800, Tao Cui wrote:
> From: Tao Cui <cuitao@kylinos.cn>
>
> ioc_rqos_done() only accounts READ and WRITE completions, so zone
> append completions are excluded from the latency window: the vrate
> feedback loop cannot see ZA-induced latency, leaving it unable to
> respond to device saturation caused by zone appends. Similarly,
> calc_size_vtime_cost_builtin() does not classify zone append as a
> write operation.
>
> Charging (the cost model) and feedback (the latency window) are
> separate mechanisms, so this is not covered by the previous patch
> that prices zone appends.
>
> Treat zone append as WRITE for both latency accounting and cost
> classification.
Can you add a blktests for this and the flush case?
next prev parent reply other threads:[~2026-09-10 5:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-08 2:21 [PATCH 0/4] blk-iocost: charge flushes and zone appends Tao Cui
2026-09-08 2:21 ` [PATCH 1/4] blk-iocost: charge flushes as pageless random writes Tao Cui
2026-09-10 5:41 ` Christoph Hellwig
2026-09-08 2:21 ` [PATCH 2/4] blk-iocost: charge zone appends as page-counted sequential writes Tao Cui
2026-09-08 2:21 ` [PATCH 3/4] blk-iocost: account zone append completions in latency stats Tao Cui
2026-09-10 5:39 ` Christoph Hellwig [this message]
2026-09-08 2:21 ` [PATCH 4/4] blk-iocost: fix stale comment in ioc_rqos_throttle() Tao Cui
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