On Sat, Apr 19, 2014 at 3:52 PM, Jon V. <sybersn...@gmail.com> wrote: > > NIO controls and deals with the selectors. Async IO is a part of that but > is not the same thing. Async io means that if a write cannot be fully > flushed. It will not block until it can be. NIO provides us the events to > tell us that data is available in the socket.
Async IO is the ability for a single thread to perform (multiplex) IO (connect, read, write, close etc..) for multiple file descriptors. As far as I know, without NIO you cannot achieve that in Java. There is no sense in read or write without blocking if you cannot wait (vs actively poll) for an event. > On Apr 19, 2014 4:56 AM, "Alon Bar-Lev" <alon.bar...@gmail.com> wrote: > > > On Sat, Apr 19, 2014 at 10:58 AM, Emmanuel Lécharny <elecha...@gmail.com> > > wrote: > > > Le 4/19/14 9:45 AM, Alon Bar-Lev a écrit : > > >> On Sat, Apr 19, 2014 at 10:38 AM, Emmanuel Lécharny < > > elecha...@gmail.com> wrote: > > >>> Le 4/19/14 9:13 AM, Alon Bar-Lev a écrit : > > >>>> Hi, > > >>>> > > >>>> The mission of async is to avoid having threads at all, or at least > > O(1). > > >>>> > > >>>> As you have underline internal/private low level channels for socket > > >>>> processing, and public high level channels to communicate with > > >>>> application, there should be a mechanism for library to request wake > > >>>> up for these low level channels. > > >>>> > > >>>> Another option is to avoid using sockets at all within the > > >>>> implementation and require application to manage the sockets and pipe > > >>>> socket data into the library. > > >>>> > > >>>> I understand this is conceptional change than what we have now, but > > >>>> this what will enable scale without abusing system threads or have > > >>>> nondeterministic behaviour in high load. > > >>> There are a few important things you have to know about async and > > threads : > > >>> - the extra cost for dealing with async connection is around 30%. That > > >>> all but free > > >>> - a standard system can easily deal with a few thousands of threads > > >>> > > >>> Now, unless you define what is "high load", I don't really see what > > kind > > >>> of advantage we can get with an async implementation. > > >>> > > >>> FTR, when MINA was initially created, it was because there was a need > > >>> for a system supporting potentially ten of thousands of connections. Is > > >>> that what you are targetting ? > > >> Yes, using work threads that are derived per # of CPUs, no more. > > >> I am far from the pure "Java" world... but if async IO is 30% > > >> insufficient, maybe it worth to use libssh (C) and communicate with it > > >> using single socket from java, delegating IO outside of java. > > > IO are already delegated outside on Java. Eveything IO related is > > > written in C and wrapped into Java class. > > > > > > The extra cost when using NIO is due to the management of SelectorKey > > > lists (with the various steps involved when dealing with those lists). > > > > > > All in all, when it comes to process IO, Java does not really add some > > > extra cost over a plain C implementation. It's not the same story when > > > using NIO, especially when dealing with many concurrent connections. > > > > > > > So I am confused... Java does not add cost to async IO, but NIO does? > > While NIO is the only interface to Java async IO? > >
