Re^5: Better "IPC" method than BDB?

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.

I'm not really a human, but I play one on earth. Cogito ergo sum a bum

Comment on Re^5: Better "IPC" method than BDB?

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Re^6: Better "IPC" method than BDB? by samtregar (Abbot) on May 24, 2007 at 17:38 UTC
I would be willing to bet that SysV shared-mem is faster than threads-shared-mem Really? How much would you bet? I think this could be a money maker for me! SysV shared memory is a lot slower than most people think. IPC::Sharelite is about as fast as using Storable to read and write files on disk! -sam	[reply]
Re^7: Better "IPC" method than BDB? by zentara (Cardinal) on May 25, 2007 at 12:33 UTC
From what I gather, threads-shared-memory has to be copied once when it is read, that alone will make it slower by a millisec or 2, in my guestimation. But I'm just an intuitive zen hacker, not a OS engineer. If you have some bechmark code please post it. A "subjective" view of how fast something is, can be very deceiving when dealing with millisecond differences, since the human brain works at such a slow speed. So I will stand by what I said, since all books claim (with justification) that shared memory is the fastest form of IPC. It is up to you to prove otherwise, since you challenge the conventional wisdom. It is similar to the argument whether interpreted code runs as fast as compiled code..... if you put it on a 2Ghz machine, you can't tell the difference, but there is a minute one. As far as shared memory being faster than a Berkeley Database, I think that is almost assured. How can calls to a disk-based database server be faster than reading directly from RAM? (Assuming a properly built system, and correctly written code) I'm not really a human, but I play one on earth. Cogito ergo sum a bum	[reply]
Re^8: Better "IPC" method than BDB? by samtregar (Abbot) on May 25, 2007 at 21:31 UTC
Sorry, no time to waste on this running benchmarks for you. You can keep believeing what you read in books if you want, it doesn't matter much to me. If you're curious about where I got my results, it was during development of HTML::Template. It supports caching in memory, disk and SysV shared memory. Shared memory turned out to be so slow it was hardly worth the implementation effort. And that's it, I'm done with this thread! -sam	[reply]