From: Christoph Hellwig <hch@infradead.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Peter Chang <dpf@google.com>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
linux-ide@vger.kernel.org
Subject: Re: [PATCH] set a base index for libsas based ata devices
Date: Wed, 21 Dec 2016 00:03:42 -0800 [thread overview]
Message-ID: <20161221080342.GA21557@infradead.org> (raw)
In-Reply-To: <1482258634.2475.20.camel@HansenPartnership.com>
On Tue, Dec 20, 2016 at 10:30:34AM -0800, James Bottomley wrote:
> I'd actually disagree with this assertion; it's why tagging (what you
> mean by ncq) and queue depth are separate. Queue depth represents the
> number of outstanding commands we sent on the wire; however, it often
> excludes things like sense probes and error handling commands, so
> tagged depth==1 is a different operating environment from untagged.
> Some transports actually have no untagged variant nowadays, so it's
> physically impossible to disable tagging.
Yes. We have the queue_type sysfs file that also used to be writeable
and allow changing the queue type, but it's never been used for
anything.
For debugging you can clear the tagged_supported flag in the driver,
but there should be no reason for doing that during normal operation
for a SAS HBA driver.
prev parent reply other threads:[~2016-12-21 8:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-20 18:15 [PATCH] set a base index for libsas based ata devices Peter Chang
2016-12-20 18:30 ` James Bottomley
2016-12-21 8:03 ` Christoph Hellwig [this message]
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