On Tue, Apr 10, 2012 at 4:21 AM, Daniel Bünzli <daniel.buen...@erratique.ch> wrote: > Anil, > > Thanks for the analysis. > >> The I/O loop is being called twice for the non-blocking version, as it >> receives >> the `Await signal, does the Unix syscall, and then jumps into decode_src. >> Presumably >> a full non-blocking version would have to register with a select handler if >> it >> gets an EAGAIN at this point, > > > Yes. > >> In terms of the number of system calls, the non-blocking one is more >> efficient, >> as it uses a 16KB buffer versus the 4K reads done by the blocking version. > > > Yes, the 4K reads are a limitation of pervasives channels. For each mechanism > I used the largest buffer that the OCaml runtime uses. > >> Looking at the two decoders in src/se.ml, it looks like the non-blocking one >> allocates closures on every loop, which the blocking one doesn't. This is so >> it >> can store the continuation in d.k for the next loop. > > > Yes, that's a side effect of writing in continuation passing style in general > since continuations are often partially applied functions.
I believe this particular performance issue is fixed in the upcoming 4.0 release, based on some work by OCamlPro. >> So to summarise, instead of storing a continuation closure, it would >> probably be better >> to explicitly store the state in d.k to minimise allocation? > > > Maybe, but keep in mind that s-expressions are very simple to parse. It may > be obvious in this case but depending on what you decode defining/storing the > state may become complex. Cps is an easy and general way to solve the problem > while keeping the whole thing reasonably readable. But do you maybe see > another pattern that I don't ? > >> The library looks very useful by the way: I have exactly the same issue with >> several >> Lwt-only protocol libraries we're developing at the moment. Would love to >> use yours before >> the first release of them to make them more independent of the underlying >> I/O mechanism... > > > That would be nice, I'm glad if you can somehow reuse the pattern. > > > Best, > > Daniel > > -- > Caml-list mailing list. Subscription management and archives: > https://sympa-roc.inria.fr/wws/info/caml-list > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > Bug reports: http://caml.inria.fr/bin/caml-bugs > -- Caml-list mailing list. Subscription management and archives: https://sympa-roc.inria.fr/wws/info/caml-list Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs
