On Dec 3, 2008, at 3:45 PM, Bruno - e-comBR wrote:
I want to know how much Apache's HTTPD takes the advantages of multiple CPUs. Is there any difference about performance betwen using worker or prefork as MPM??
Depends on your operating system architecture. However, in any situation the design of the most popular Apache MPMs has each worker handling a particular connection from beginning to end. This is the case whether workers are pre-forked processes, or whether they are threads in a child process (worker, Windows MPM). Effectively this means that most of the time, workers are waiting for something to do: waiting to read something from the network, for the backend to return data, etc. This means that you usually run many more workers than you have CPU cores.
Being a little "out of topic", let me ask you... On a Linux SMP system, does a n Core processor works like n processors?? Is there any differences taking performance advantages of multiple CPUs betwen using multiple threads or multiple processes??
On Linux specifically, you have two factors at work: 1) Linux process structures are relatively lighweight2) As far as the Linux kernel is concerned, each thread is mapped onto a process structure
The last one means you don't win performance by going to threads instead of staying with processes, and the first one means that the penalty of context-switching between many processes is smaller on Linux than on some other systems (like Solaris).
Just to make you understand the issue, I'm want to setup a dedicated web server with two Quad Core processors, and I can't use worker(which is multi-threaded) because I'm using mod_php. So, what I really want to know: it's a fact that many CPU's(2 processors x 4 cores = 8) will improve the processing performance??
Actually, I believe the core of PHP is now threadsafe and re-entrant. However, the PHP group can't make any assumptions or claims about threadsafety of the libraries PHP uses, so they won't state PHP runs under multithreaded MPMs. And, because of the circumstances discussed above, there is no practical gain from running threads on Linux so PHP has little motivation to improve this situation.
HtH, S. -- Sander Temme sctemme@xxxxxxxxxx PGP FP: 51B4 8727 466A 0BC3 69F4 B7B8 B2BE BC40 1529 24AF
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