Hi, I am in the process of writing an application which is a central manager which should do a lot of IPC with databases, worker processes (already written in C, receiving commands via UNIX sockets), and user control via another UNIX socket.
Initially I tried using nonblocking IO, but I found a lot of headaches finding out the state of the different filehandles (I think they aren't well suited for nonblocking IO). The next step would be to use select loop and low-level IO, but it scared me a bit :) Also I tried POE, but didn't have nothing near good performance. Then threads came as a natural solution as I could have different subs doing blocking IO without worring (a similar approach I used for the workers, many of them blocking, not consuming CPU and being very tiny in size). But then I found out the new ithreads, which seem to me unacceptably big, but since I will use just 4 or 5, I can cope with that. My first problem is, I don't understand yet the inner workings, and I've seen different behaviors in debian sarge and woody; but the most troubling thigs is I find dead IPC shared memory blocks which sometimes I can't even free with ipcrm!! I don't understand why use IPC in the first place, there isn't any option to use real shared memory (they are threads!), or shm_open+mmap? (not sure if it is possible under perl) Also, I found today the Elizabeth Mattijsen's forks.pm module, and read that it uses TCP communication (why not UNIX, or -again- mmap?). Anyway, that seems to me the best approach, as it would be lighter than ithreads, and I just need to pass messages and a couple of shared variables across threads. I read a little of the code but couldn't understand anything :). I'm very worried about performance issues, and some hints would be useful before deciding what to use for the project. Having spent many hours trying to figure out what to do, there is very little stopping me from trying a complete C solution, but that would be painful! Please, give me some hints so I can still be a lazy perl lover :) Thanks a lot for your time! -- Martín Ferrari
