Well, how can IPC where ram memory is actually shared between apps be slower? It must be in your implementation or your kernel. I agree though, it can be tricky to use. Read Chapter 5 of ALP
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I don't know the real answer but I suspect it has to do with modern file-systems being very well tuned, with fancy memory caches that are actually better than old-school SysV shared memory. For me it doesn't really matter why it's slow unless I expect to fix it. Fixing SysV shared-memory would a complete waste of time, I think!
-sam
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Fixing SysV shared-memory would a complete waste of time, I think! I tend to agree, I've only used it as a learning experience. I tend to go with threads-shared-memory. IIRC SysV shared mem had a nasty habit of not destroying itself automatically, leaving these security gaps if you are not careful. I have seen some patches that address this problem, but threads are my first choice of tool now. I would be willing to bet that SysV shared-mem is faster than threads-shared-mem, if proper tests were done, but if you really need that kind of millisec speed increase, you should write it in c or assembly :-) . Of course, if you have to fork, instead of threading, SysV Shared mem still provides a good way of IPC between forked processes.
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