From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: RE: [PATCH] aic94xx: fix routing algorithms Date: Tue, 11 Jul 2006 08:54:43 -0400 Message-ID: <1152622483.3575.11.camel@mulgrave.il.steeleye.com> References: <16C8363E16D7234AB844FDB52D4AEA650C2DB6@ntserv.PacificCodeWorks.local> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat9.steeleye.com ([209.192.50.41]:32976 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S1751274AbWGKMyx (ORCPT ); Tue, 11 Jul 2006 08:54:53 -0400 In-Reply-To: <16C8363E16D7234AB844FDB52D4AEA650C2DB6@ntserv.PacificCodeWorks.local> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Robert Tarte Cc: linux-scsi On Tue, 2006-07-11 at 01:30 -0700, Robert Tarte wrote: > [Tarte, Robert] There is a very specific algorithm for programming the > routing tables to avoid routing table thrashing in a mixed OS / > adapter > multi-initiator environments (the last one I looked at was from the > SAS-1.1 draft, sas1r07.pdf, project T10/1601-D, > SASDiscoverSimulation.cpp or see section 4.8.7). I had always assumed > that the original route table configuration code adhered to that > algorithm. Has this patch been verified against that algorithm? Or > does it now come up with the exact same route tables as mptsas? When > you > say table routed ports, you mean that both the upstream and down > stream > expanders are configured as table routed? No ... this is the programme in annex L of sas-2, isn't it? Even if it were available somewhere, the aic94xx doesn't yet have the necessary SMP tap to try it. The problem it's solving, which is legal under the sas2 standard is S->T routing (not T->T which is technically illegal under the standard, but which this change will also make possible). If an expander configuration is set up in the recommended cascade (i.e. T->S) then this addition will never even be activated, so the change doesn't modify the existing algorithm for the pure and recommended T->S cases. And yes, you're right, I'm gearing up to test this out multi-initiator (when I actually get the right cables) ... and since I don't have a fanout expander, my configuration is going to have to be HBA --------- Edge Expander ----------- Edge Expander ---------- HBA | | Device Device James James