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SubjectRe: epoll,threading
Date
Hi Arunachalam,

On Saturday 26 May 2007, Arunachalam wrote:
> I want to know in detail about , what the events (epoll or /dev/poll or
> select ) achieve in contrast to thread per client.
>
> i can have a thread per client and use send and recv system call directly
> right? Why do i go for these event mechanisms?

Try 30.000 clients or more on a x86 32bit box.
That will show you the difference quite nicely :-)

More seriously: Thread per client scales only to a certain amount of clients
per RAM. If you like to scale beyond that to like to minimize your state
per client. If you have a thread then you have a task structure as
unswappable memory in kernel, a per-thread stack, which is reducing
your virtual memory per process (you have only around 3GB of virtual
memory per process in Linux x86 32bit).

So one uses a process or thread pool to scale beyond that.
Pool size is typically related to the amount of CPU cores in the system.

Regards

Ingo Oeser

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