From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ira Weiny Subject: Re: Default force_link_speed value in opensm configuration Date: Tue, 13 Oct 2009 12:44:48 -0700 Message-ID: <20091013124448.208cf778.weiny2@llnl.gov> References: <4ACB6891.7010202@gmail.com> <20091006142728.3d1e5bcc.weiny2@llnl.gov> <4AD2FB39.6040602@gmail.com> <20091012143553.04554689.weiny2@llnl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Hal Rosenstock Cc: "Eli Dorfman (Voltaire)" , OFED mailing list List-Id: linux-rdma@vger.kernel.org On Tue, 13 Oct 2009 09:39:08 -0400 Hal Rosenstock wrote: > On Mon, Oct 12, 2009 at 5:35 PM, Ira Weiny wrote: > > On Mon, 12 Oct 2009 11:47:37 +0200 > > "Eli Dorfman (Voltaire)" wrote: > > > >> Ira Weiny wrote: > >> > On Tue, 06 Oct 2009 17:56:01 +0200 > >> > "Eli Dorfman (Voltaire)" wrote: > >> > > >> >> Hi, > >> >> > >> >> Is there a reason for setting default force_link_speed to 15 (set enabled as supported) > >> >> and not to 0 (don't modify PortInfo:LinkSpeedEnabled )? > > This is going back some 2 years to 7/15/07 commit ID > c7cbf11992b111d2b9c7347e398e67f2b5806edb > > commit c7cbf11992b111d2b9c7347e398e67f2b5806edb > Author: Hal Rosenstock > Date: Sun Jul 15 06:43:20 2007 -0400 > > OpenSM: Change force_link_speed to allow for local policy and more flexibili > > OpenSM: Change force_link_speed to allow for local policy and more > flexibility > > Extend (and change) the use of force_link_speed as follows: > 0 - no change > 1 - set to SDR > 15 - set as supported (default) > (Non zero values are used to set LinkSpeedEnabled component in PortInfo) > > Note that force_link_speed 0 which used to force SDR is now > force_link_speed 1 > > "Ideally", there were be a per port configuration of this. BTW I have a patch which allows a user to except some nodes from this restriction. I don't know that anyone but us is using this "feature" so I did not submit the patch. If someone else would like some finer granularity I can clean up the patch and make it available. > > [Note this is largely untested.] BTW, now, this is highly tested, to force SDR, on some of our clusters! Thanks! > > Signed-off-by: Hal Rosenstock > > I think that the default was chosen based on IBA 1.2.1 vol 2 p. 108 stating: > "The default value following power on shall be set to LinkSpeedSupported." > which should not be an issue with compliant hardware. > [snip] > > > > However, I would like to know if anyone else knows of hardware which needs it > > set to "15". If so, this is going to be an interesting problem... ;-) > > I'm not sure about need but I think there is a tradeoff here in > changing this. The pro is it will work with non compliant hardware. > The con is that it may result in less than the max LSS being used in > some scenarios. > > Should the default be changed for non compliant hardware or should > this need to be configured in subnets including such hardware as it > has since this was introduced ? > I think that is a good way of thinking about things. Ira -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html