Re: cfq: depth 4 reached, tagging now on

Jens Axboe
2005-02-21T08:20:51Z

On Sat, Feb 19 2005, Lee Revell wrote:
> Starting around 2.6.11-rc4 I get this printk during the boot process
> after kjournald starts, and again if I stress the filesystem.
>
> cfq: depth 4 reached, tagging now on
>
> Is this printk intentional? I am sure users will wonder about it,
> especially because (presumably) cfq turns tagging off at some point in
> between, and doesn't say anything about it.

It is intentional, but could be supressed. But I'm wondering if the
accounting change introduced a bug - what hardware are you using cfq on
(ie does it actually do tagged command queueing, is it SCSI?)?

It's a one-time message. CFQ starts out assuming the drive doesn't do
TCQ, if the driver depth goes beyond a defined limit (4), it will assume
that the hardware can do tagged queueing and change its internal
accounting accordingly. The setting stays that way, it's not a
transitional state.

--
Jens Axboe