From: Christoph Hellwig <hch@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: Tao Cui <cui.tao@linux.dev>, Josef Bacik <josef@toxicpanda.com>,
josef@toxicopanda.com, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, cuitao@kylinos.cn
Subject: Re: [PATCH v2 1/4] blk-iocost: charge flushes as pageless random writes
Date: Mon, 21 Sep 2026 00:06:11 -0700 [thread overview]
Message-ID: <arDXYwNm7rGqB7pg@infradead.org> (raw)
In-Reply-To: <9575357186118be214d6377dd80a21e8@kernel.org>
On Sat, Sep 19, 2026 at 04:59:51AM -1000, Tejun Heo wrote:
> Hello, Tao.
> Pricing a flush as a random write, or as a page where that comes out to
> zero, is as arbitrary as pricing it at zero,
No, it absolutely is not. For any flush that actually makes here it
is extremely expensive, and 0 is the wrongest possible value. Even
batching does not change that, as batching is not actually effective
in any normal file system workload.
next prev parent reply other threads:[~2026-09-21 7:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 8:53 [PATCH v2 0/4] blk-iocost: charge flushes and zone appends Tao Cui
2026-09-16 8:53 ` [PATCH v2 1/4] blk-iocost: charge flushes as pageless random writes Tao Cui
2026-09-18 13:21 ` Christoph Hellwig
2026-09-19 14:59 ` Tejun Heo
2026-09-20 7:08 ` Tao Cui
2026-09-20 12:19 ` Tejun Heo
2026-09-21 7:06 ` Christoph Hellwig [this message]
2026-09-21 16:58 ` Tejun Heo
2026-09-16 8:53 ` [PATCH v2 2/4] blk-iocost: charge zone appends as page-counted sequential writes Tao Cui
2026-09-18 13:22 ` Christoph Hellwig
2026-09-20 7:11 ` Tao Cui
2026-09-19 15:00 ` Tejun Heo
2026-09-20 7:13 ` Tao Cui
2026-09-16 8:53 ` [PATCH v2 3/4] blk-iocost: account zone append completions in latency stats Tao Cui
2026-09-18 13:22 ` Christoph Hellwig
2026-09-16 8:53 ` [PATCH v2 4/4] blk-iocost: fix stale comment in ioc_rqos_throttle() Tao Cui
2026-09-18 13:23 ` Christoph Hellwig
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