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Date:   Tue, 17 Jan 2023 00:13:44 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
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Subject: Re: [PATCH v2 07/18] block: introduce duration-limits priority class
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On Tue, Jan 17, 2023 at 05:06:52PM +0900, Damien Le Moal wrote:
> They can, by using a large limit for "low priority" IOs. But then, these
> would still have a limit while any IO issued simultaneously without a CDL
> index specified would have no limit at all. So strictly speaking, the no
> limit IOs should be considered as even lower priority that CDL IOs with
> large limits.
> 
> The other aspect here is that on ATA drives, CDL and NCQ priority cannot
> be used together. A mix of CDL and high priority commands cannot be sent
> to a device. Combining this with the above thinking, it made sense to me
> to have the CDL priority class handled the same as the RT class (as that
> is the one that maps to ATA NCQ high prio commands).

Ok.  Maybe document this a bit better in the commit log.