On Tue, 21 Apr 2009 10:50:18 EDT erik quanstrom <quans...@quanstro.net> wrote: > On Tue Apr 21 10:34:34 EDT 2009, n...@lsub.org wrote: > > Well, if you don't have flush, your server is going to keep a request > > for each process that dies/aborts.
If a process crashes, who sends the Tflush? The server must clean up without Tflush if a connection closes unexpectedly. I thought the whole point of Tflush was to cancel a potentially expensive operation (ie when the user hits the interrupt key). You still have to cleanup. > > If requests always complete quite > > soon it's not a problem, AFAIK, but your server may be keeping the > > request to reply when something happens. Also, there's the issue that > > the flushed request may have allocated a fid or some other resource. > > If you don't agree that the thing is flushed you get out of sync with the > > client. > > > > What I mean is that as soon as you get concurrent requests you really > > ned to implement flush. Again, AFAIK. > > isn't the tag space per fid? a variation on the tagged queuing flush > cache would be to force the client to make sure that reordered > flush tags aren't a problem. it would not be very hard to ensure that > tag "overlap" does not happen. Why does it matter? > if the problem with 9p is latency, then here's a decision that could be > revisisted. it would be a complication, but it seems to me better than > a http-like protocol, bundling requets together or moving to a storage- > oriented protocol. Can you explain why is it better than bundling requests together? Bundling requests can cut out a few roundtrip delays, which can make a big difference for small files. What you are talking about seems useful for large files [if I understand you correctly]. Second, 9p doesn't seem to restrict any replies other than Rflushes to be sent in order. That means the server can still send Rreads in any order but if a Tflush is seen, it must clean up properly. The situation is analogous what happens in an an OoO processor (where results must be discarded in case of exceptions and mis-prediction on branches).
