Quoting r. Rimmer, Todd <[EMAIL PROTECTED]>: > Subject: RE: [openib-general] [PATCH] osm: PathRecord prefer 1K MTU for > MT23108 devices > > > From: Eitan Zahavi [mailto:[EMAIL PROTECTED] > > Sent: Monday, September 18, 2006 11:20 AM > > To: Rimmer, Todd > > Cc: Or Gerlitz; Michael S. Tsirkin; OPENIB > > Subject: Re: [openib-general] [PATCH] osm: PathRecord prefer 1K MTU > for > > MT23108 devices > > > > Hi Todd, > > > > Seems like your knowledge about the specific MTU best for the > > application (MPI) you are running is good > > enough such that you will be able to include the MTU in the PathRecord > > request and thus the patch describe in here will not affect your MPI > at > > all. > > The patch only applies if your request does not provide any MTU & MTU > > SEL comp_mask > > Eitan, > > The question is not about "our MPI", rather its to ensure the Open > Fabrics and OFED included MPIs and ULPs are capable of being tuned for > optimal performance. When a fabric runs more than 1 application, its > necessary to be able to tune this at the MPI, SDP, etc level, not at the > SM level.
We did not remove this ability at all. So it's there. > This patch turns on a non-standard behaviour in the SM for the entire > fabric such that some applications will have better performance while > others will suffer. I disagree. The behaviour is perfectly standards compliant. > In order to be complete, this patch would need to > include ULP level tunability in all the relevant ULPs (MPI, SDP, uDAPL, > etc) to select the "MAX MTU" to use or to request. This tunability is already there - that's what MTU selector in path queries does. > This then begs the question, if proper tuning requires all the ULPs to > have a configurable MAX MTU, why should the SA need to implement the > quirk at all? > > Todd Rimmer If ULP wants MAX MTU, it must set MTU selector to 3 in path query. If MTU selector is disabled in the query, SM will guess which MTU is best to select. SM used a specific heuristic to perform that guess. All we did is, provide an option to use a different heuristic. This is useful because, SM has data on the whole fabric as opposed to ULPs which often only have data on the endnode. -- MST _______________________________________________ openib-general mailing list openib-general@openib.org http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
