J. Peng wrote:
Apache with prefork mode can share the memory? Sorry I didn't know it. Sharing memory between multi-processes need extra programming, I don't know apache has done it already.
Both prefork and worker models share memory. fork() takes all of your pages and marks them "copy on write". This means; no-touchie, share nice. Don't confuse this with shared, writeable pages. Once you do write to any byte of a common page (even assigning the same value and not actually anything), the kernel makes you up your own private copy. Do that in every fork()ed child, and it hurts. This is why the process and conf pools of httpd should never be touched by a sane module from the child_init hook, onwards. But you won't notice the sharing as much with worker model, since there might be only 10 processes sharing memory to support 250 children, instead of 250 children all sharing that same config. Although worker starts out 25 times more compact, so the net win from fork()+threading is roughly equivalent ;-)
