From owner-freebsd-scsi Wed Nov 10 14:52:46 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from front4m.grolier.fr (front4m.grolier.fr [195.36.216.54]) by hub.freebsd.org (Postfix) with ESMTP id 5B8F314CA3 for ; Wed, 10 Nov 1999 14:52:38 -0800 (PST) (envelope-from groudier@club-internet.fr) Received: from localhost (ppp-159-141.villette.club-internet.fr [195.36.159.141]) by front4m.grolier.fr (8.9.3/No_Relay+No_Spam_MGC990224) with SMTP id XAA18278; Wed, 10 Nov 1999 23:52:28 +0100 (MET) Date: Thu, 11 Nov 1999 01:16:12 +0100 (MET) From: Gerard Roudier X-Sender: groudier@localhost To: "Justin T. Gibbs" Cc: Nick Hibma , scsi@FreeBSD.ORG Subject: Re: queues in CAM In-Reply-To: <199911102059.NAA77778@narnia.plutotech.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Wed, 10 Nov 1999, Justin T. Gibbs wrote: > In article you = wrote: > >=20 > > I'm trying to understand the queueing thing in CAM. The following code > > fragment (which is found in all the SIMs) > >=20 > >=20 > > devq =3D cam_simq_alloc(MO /*maximum openings*/); > > sc->sim =3D cam_sim_alloc(umass_cam_action, umass_cam_poll, > > =09=09=09=09"umass", sc, > > device_get_unit(sc->sc_dev), > > =09=09=09=09MDO /*max_dev_openings*/, > > =09=09=09=09MTDO /*max_tagged_dev_openings*/, > > =09=09=09=09devq); > >=20 > > confuses me. Are the MDO and MTDO values related to per device queues? > > And is the MO value related to a per SIM queue? >=20 > Yes and yes. Some controllers, although they can accept a rather large > number of transactions, cannot queue that many to just a single device. And some controllers may want to accept more than 256 transactions and then have to be careful of not queuing all the transactions to a single=20 device. =20 G=E9rard. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message