Date: Thu, 11 Nov 1999 01:16:12 +0100 (MET) From: Gerard Roudier <groudier@club-internet.fr> To: "Justin T. Gibbs" <gibbs@narnia.plutotech.com> Cc: Nick Hibma <hibma@skylink.it>, scsi@FreeBSD.ORG Subject: Re: queues in CAM Message-ID: <Pine.LNX.3.95.991111010546.506B-100000@localhost> In-Reply-To: <199911102059.NAA77778@narnia.plutotech.com>
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On Wed, 10 Nov 1999, Justin T. Gibbs wrote: > In article <Pine.BSF.3.96.991110070739.6087C-100000@henny.plazza.it> you wrote: > > > > I'm trying to understand the queueing thing in CAM. The following code > > fragment (which is found in all the SIMs) > > > > > > devq = cam_simq_alloc(MO /*maximum openings*/); > > sc->sim = cam_sim_alloc(umass_cam_action, umass_cam_poll, > > "umass", sc, > > device_get_unit(sc->sc_dev), > > MDO /*max_dev_openings*/, > > MTDO /*max_tagged_dev_openings*/, > > devq); > > > > confuses me. Are the MDO and MTDO values related to per device queues? > > And is the MO value related to a per SIM queue? > > 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 device. Gérard. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the messagehelp
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