Re: Shared memory IPC using NIO memory-mapped files -- anyone done this?

At 08:19 AM 8/18/2007, you wrote:
>Memory mapped files are not the way to got about this. Having to write
>everything to disk would kind of kill your "high performance" requirement.
>:)

Allegedly, using memory-mapped files the disk IO 
is spared -- or maybe I just have the wrong idea about that?

Brian Maso


>You'll need JNI code which wraps unix domain sockets. If that isn't fast
>enough, wrap true shared memory with JNI. Use shared memory to actually
>share the data and the sockets to coordinate between processes.

OK, so use more traditional IPC mechanism to 
coordinate the consumer/processor choreography. I 
thought maybe that would be the case, but wanted to make sure. Thanks!



>I would start off with network sockets. If those aren't fast enough, they'll
>be easy enough to replace w/ domain sockets (the native API is identical).




>Bob
>
>On 8/18/07, Brian Maso <[email protected]> wrote:
> >
> > Java NIO supports memory-mapped files, which has the cool ability to
> > allow multiple apps to share the same array of data if they all map
> > the same file in to their respective address spaces.
> >
> > I've wondered about using memory-mapped files for inter-process
> > communication for a while. Someone I know is asking me whether or not
> > this is good to use for high-performance communication between Java
> > and C++ -- basically sharing fixed-length records between Java and a
> > C/C++ program in a producer/consumer sort of system.
> >
> > It seems like memory-mapped files would be ideal for sharing data
> > like this. A Java app could extract data from some source and put it
> > in to a MappedByteBuffer, which would immediately be visible to any
> > other app on the same box that has mapped the same file. However, I
> > can't figure out how the Java process would "signal" the external
> > app, indicating that a new record is available for consumption, or
> > alternatively how an external app would signal the Java app to tell
> > it to write out a new record to the shared memory space.
> >
> > Anyone familiar with shared memory inter-process communication out
> > there who can give me a hint? Google and the regular sources aren't
> > revealing anything to me this morning.
> >
> > Brian Maso
> >
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