From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Khapyorsky Subject: Re: [infiniband-diags] [PATCH] [2/2] split out scan specific data from ibnd_node_t Date: Fri, 13 Nov 2009 00:59:56 +0200 Message-ID: <20091112225956.GA7192@me> References: <1257190401.580.31.camel@auk31.llnl.gov> <1257196316.580.33.camel@auk31.llnl.gov> <20091106181633.GQ7192@me> <1257532494.18550.89.camel@auk31.llnl.gov> <20091112163105.GI7192@me> <20091112105930.4248e521.weiny2@llnl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20091112105930.4248e521.weiny2-i2BcT+NCU+M@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ira Weiny Cc: Al Chu , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org Hi Ira, On 10:59 Thu 12 Nov , Ira Weiny wrote: > > nodesdist was remove from the public interface. Although an "advanced" user > might have been able to use it, the data stored there was very scan specific. > Removing it was a good idea for 2 reasons, 1) simplify the interface, I don't see how this conceptually simplifies interface. I think that it started from a wrong approach about having two data structure sets - public and private. Now it requires cleaning again and again in order to have simpler interface. > 2) if > the scan algorithm changed users might have to change the way they use the > data; not good for compatibility. Maybe, but let him to decide. Such usage is not mandatory. > I agree there was some usefulness, sometimes. However the path_portid can not > be guaranteed to be valid. Why not? Isn't it a valid on the last scan? > Again there are multiple issues. First I don't > think we want to support to this to the users. But you don't need to support it. Advanced use is developer's responsibility. > Second Al is working toward is > the ability to cache the fabric information to be read back later. Storing > all this "scan" specific information is going to be extra work which is > superfluous to the layout of the fabric. Hard to say really without seeing any code, but you can simply keep all this scan specific information over session and have a pointer field on ibnd_fabric structure which refer this. > > I cannot understand why are you trying to make things there as "private" > > as technically possible (even on price of extra code size and > > complexity). Finally it is an open source stuff, so let to users to use > > it how they want and for their own responsibility. :) > > Making things "private" allows us to change the library without breaking the > interface. I don't think > Furthermore, it simplifies the interface for users who want to > write code at a higher level. I'm not asking to make high level life harder :). My point is to not prevent from advanced developers to use available low level too, especially when such preventing requires some extra efforts. > My original design goals were 2 fold. 1. make > a library which speeds up the functionality of the perl script tools. 2. > Provide a C interface to a fast scan library which can be used to implement > further tools which would have formerly been implemented via scripts around > ibnetdiscover. My purposes serve (2) very well. Isn't it? > > Here is one use case we have been working off of. > > One of our MPI developers here is not familiar with Infiniband. He has > written many scripts around the current suite of tools for various research > that he does. The concepts of nodes, ports, and links are familiar to him but > sending a "MAD" or differentiating between a GSI MAD vs SMP is not. I want to > give him information about nodes, links, ports, errors, data counters, routing > tables, etc. without making him use the MAD layer, or worse yet, umad layer. How having 'path_portid' in node structure enforces him to use the MAD or umad (which is simpler than mad in general, IMO) layers? It doesn't. > In this use case he does not care that libibnetdisc does a BFS and creates a > nodesdist structure of some sort resulting from that algorithm. Presenting a > "fabric" with a list of "nodes" which further have some "ports" makes sense to > a user like this. Again, how having access to internal discovery stuff makes a life of such users harder? > This use case in addition to trying to cache the data makes a simpler, cleaner > interface much more attractive. :-D And there is another use case (hypothetical yet) - one of our IB developers is familiar with infiniband... Would such "high-level"-only interface be so attractive for him? Sasha -- 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