Re: [PATCH] blk-throtl: optimize IOPS throttle for large IO scenarios

From: Tejun Heo <tj@kernel.org>
To: brookxu <brookxu.cn@gmail.com>
Cc: axboe@kernel.dk, cgroups@vger.kernel.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blk-throtl: optimize IOPS throttle for large IO scenarios
Date: Tue, 27 Jul 2021 06:21:11 -1000	[thread overview]
Message-ID: <YQAydzEhZfPUpzWI@mtj.duckdns.org> (raw)
In-Reply-To: <34a6f4b5-9055-e519-5693-068f8dcb169c@gmail.com>

Hello,

On Tue, Jul 27, 2021 at 11:06:18AM +0800, brookxu wrote:
> Make blk-throttle use rq-qos may be more elegant. But I found that there may be at least
> one problem that is difficult to solve. blk-throttle supports separate throttle for read
> and write IOs, which means that we cannot suspend tasks during throttle, but rq-qos
> throttle IOs by suspending tasks.

Ah, right, I forgot about that.

> We may be able to relocate the blk-throttle hooks to the rq-qos hooks. Since we may not
> be able to replace the throttle hook, in this case, if we register a rq-qos to the system,
> part of the blk-throttle hooks is in rq-qos and part hooks not, which feels a bit confusing.
> In addition, we may need to implement more hooks, such as IO merge hook.

Would it be possible to just move the blk-throtl throttling hook right next
to the rq-qos hook so that it gets throttled after splitting?

Thanks.

-- 
tejun