linux-kernel - Re: [PATCH V5 08/17] blk-throttle: make throtl

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Date:   Mon, 9 Jan 2017 15:08:43 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Shaohua Li <shli@...com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, axboe@...com, vgoyal@...hat.com
Subject: Re: [PATCH V5 08/17] blk-throttle: make throtl_slice tunable

Hello,

On Thu, Dec 15, 2016 at 12:32:59PM -0800, Shaohua Li wrote:
> throtl_slice is important for blk-throttling. It's called slice
> internally but it really is a time window blk-throttling samples data.
> blk-throttling will make decision based on the samplings. An example is
> bandwidth measurement. A cgroup's bandwidth is measured in the time
> interval of throtl_slice.
> 
> A small throtl_slice meanse cgroups have smoother throughput but burn
> more CPUs. It has 100ms default value, which is not appropriate for all
> disks. A fast SSD can dispatch a lot of IOs in 100ms. This patch makes
> it tunable.
> 
> Since throtl_slice isn't a time slice, the sysfs name
> 'throttle_sample_time' reflects its character better.

Generally looks good.  I think some documentation would be great.
Also, do we wannt set it to a lower number if blk_queue_nonrot()?

Thanks.

-- 
tejun