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From: Tejun Heo <tj@kernel.org>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	yukuai3@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com
Subject: Re: [PATCH v2] blk-throttle: fix lower control under super low iops limit
Date: Fri, 28 Jun 2024 07:16:51 -1000	[thread overview]
Message-ID: <Zn7wA-C9LcjOmFe_@slm.duckdns.org> (raw)
In-Reply-To: <20240618062108.3680835-1-yukuai1@huaweicloud.com>

Sorry about the delay.

On Tue, Jun 18, 2024 at 02:21:08PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> User will configure allowed iops limit in 1s, and calculate_io_allowed()
> will calculate allowed iops in the slice by:
> 
> limit * HZ / throtl_slice
> 
> However, if limit is quite low, the result can be 0, then
> allowed IO in the slice is 0, this will cause missing dispatch and
> control will be lower than limit.
> 
> For example, set iops_limit to 5 with HD disk, and test will found that
> iops will be 3.
> 
> This is usually not a big deal, because user will unlikely to configure
> such low iops limit, however, this is still a problem in the extreme
> scene.
> 
> Fix the problem by making sure the wait time calculated by
> tg_within_iops_limit() should allow at least one IO to be dispatched.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

  parent reply	other threads:[~2024-06-28 17:16 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-18  6:21 [PATCH v2] blk-throttle: fix lower control under super low iops limit Yu Kuai
2024-06-28  3:34 ` Yu Kuai
2024-06-28 17:16 ` Tejun Heo [this message]
2024-06-28 20:55 ` Jens Axboe

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