Date: Wed, 5 Aug 2015 12:07:49 -0600 From: Scott Long <scott4long@yahoo.com> To: Sibananda Sahu <sibananda.sahu@avagotech.com> Cc: freebsd-scsi@freebsd.org, "Kenneth D. Merry" <ken@freebsd.org> Subject: Re: Max queue depth per target device??? Message-ID: <07949D93-5098-49EE-9D1A-95729269716B@yahoo.com> In-Reply-To: <f795348c312751d0cbc11a1c25fc6aee@mail.gmail.com> References: <f795348c312751d0cbc11a1c25fc6aee@mail.gmail.com>
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> On Aug 5, 2015, at 11:52 AM, Sibananda Sahu via freebsd-scsi <freebsd-scsi@freebsd.org> wrote: > > Hi All, > > > > Is the CAM layer provides per target queue depth setting? > > If yes then can anybody tell me how to implement that in the SIM driver? > > Or, if no, then is there any proposal to implement per target queue depth > in FreeBSD CAM layer, similar to that of the Linux SCSI sub-system? > For the SATA transport, CAM takes care of probing the SATA NCQ register and setting the appropriate queue depth. For the SCSI transport, CAM assumes that the drives will continue to take commands until they are full, and then will report a QUEUE_FULL status. When CAM gets that status, it adjusts the queue depth automatically. So no, there are no plans to set a simple static value like in Linux. CAM probes for it automatically, so long as the driver passes the QUEUE FULL status up correctly. Scott
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