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Newsgroups: comp.unix.bsd Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msunews!uwm.edu!vixen.cso.uiuc.edu!news.uoregon.edu!psgrain!library.ucla.edu!csulb.edu!csus.edu!netcom.com!bakul From: bakul@netcom.com (Bakul Shah) Subject: Re: Why select() returns ``exceptional'' for files? Message-ID: <bakulD2wLz4.5Gn@netcom.com> Organization: NETCOM On-line Communication Services (408 261-4700 guest) References: <3fois1$5d5@shore.shore.net> <bakulD2ss6p.7M4@netcom.com> <3fuupi$ji8@nova.netapp.com> <bakulD2un2v.JDI@netcom.com> <3g15jb$rs2@nova.netapp.com> Date: Tue, 24 Jan 1995 09:49:52 GMT Lines: 38 guy@netapp.com (Guy Harris) writes: >Bakul Shah <bakul@netcom.com> wrote: >>Polling would not scale too well. The `right' thing to do (IMHO >>and ideally speaking) is to extend NFS. On systems running >>earlier versions one would not get the new benefits but so what. >Which benefits? >If you mean the benefits of being able to run applications using selects >on exceptional conditions on files to block until the file changes, I Yes, these benefits. >suspect the effect of that would be that applications wouldn't use >selects on exceptional conditions on files to block until the file >changes, meaning that you wouldn't get those benefits even on *local* >files. I don't think that counts as a "so what" - i.e., I think you'd >have to implement block-until-change on top of Boring Old NFS V2 Without >The Extra Protocol and Boring Old NFS V3 Without The Extra Protocol, >even if you don't want to do so. Well, this is a problem any time new functionality is added to an established protocol. [It is a bit ironic that we see newer/faster modem protocols every few months or so but the `software' is getting harder and harder to change]. If you can implement this with an extra protocol for NFS V2 & NFS V3, (using polling or whatever) that'd be great. But even if you can't make it interoperate with NFS V2/V3, I think this is worth adding to NFS V4 or at least an experimental version (said he, blissfully ignoring reality!). I can sort of see a way to do this with a wart-on-the-side protocol that'd work with NFS2/3 and that does not use polling (if block-until-change is implemented on both client and server) and with polling if exception on change is not implemented on the server side. Bakul Shah <bakul@netcom.com>