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: >=20 > Hi All, >=20 >=20 >=20 > Is the CAM layer provides per target queue depth setting? >=20 > If yes then can anybody tell me how to implement that in the SIM = driver? >=20 > 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? >=20 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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