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From: Christoph Hellwig <hch@lst.de>
To: Hannes Reinecke <hare@suse.de>
Cc: linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
	Keith Busch <keith.busch@wdc.com>,
	Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH] nvme: stop mad sqsize increasing and decreasing
Date: Tue, 17 Mar 2020 13:49:19 +0100	[thread overview]
Message-ID: <20200317124919.GD12316@lst.de> (raw)
In-Reply-To: <20200313124410.39193-1-hare@suse.de>

On Fri, Mar 13, 2020 at 01:44:10PM +0100, Hannes Reinecke wrote:
> The NVMe spec only states:
> 
> "One slot in each queue is not available for use due to Head and
> Tail entry pointer definition."
> 
> It does not say that the actual queue size needs to decremented
> by one, it just means that we'll have to leave one slot free.
> So kill the mad decreasing and increasing of sqsize, leave it
> at the specified size, and only decrement the tagset by one to
> ensure we leave one slot free.

Not sure what is mad here.  All the *qsize values are 0s based
values on the wire, so the on the wire value need to be one
lower than the proper value.

Maybe we need to0sb / from0sb helpers to document these annoying
things a little better?  (%#^#Y@$ NVMe designers for burdening
us with this bullshit..)

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  reply	other threads:[~2020-03-17 12:49 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-13 12:44 [PATCH] nvme: stop mad sqsize increasing and decreasing Hannes Reinecke
2020-03-17 12:49 ` Christoph Hellwig [this message]
2020-03-17 15:38   ` Hannes Reinecke

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