Re: Default force_link_speed value in opensm configuration

[Hal Rosenstock <hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Tue, Oct 13, 2009 at 3:44 PM, Ira Weiny <weiny2-i2BcT+NCU+M@public.gmane.org> wrote:
> On Tue, 13 Oct 2009 09:39:08 -0400
> Hal Rosenstock <hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>> On Mon, Oct 12, 2009 at 5:35 PM, Ira Weiny <weiny2-i2BcT+NCU+M@public.gmane.org> wrote:
>> > On Mon, 12 Oct 2009 11:47:37 +0200
>> > "Eli Dorfman (Voltaire)" <dorfman.eli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> >
>> >> Ira Weiny wrote:
>> >> > On Tue, 06 Oct 2009 17:56:01 +0200
>> >> > "Eli Dorfman (Voltaire)" <dorfman.eli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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 <halr-smomgflXvOZWk0Htik3J/w@public.gmane.org>
>> 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.

There are others. This would be a worthwhile improvement IMO.

-- Hal

>
>>
>>     [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 <hal.rosenstock-Re5JQEeQqe8@public.gmane.orgm>
>>
>> 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
>
>
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