Re: Yet another I/O modeling

["" <pmarques@grupopie.com>]

Quoting Neil <neil@qlsc.sdu.edu.cn>:

> hi,all
> select/poll I/O modeling is fast,easy to use,it returns the number of fd 
> which are acitvity,but you should scan the fd array to find which fd is 
> ready,it costs a lot of time on a heavy load server.
> 
> I proposal another I/O modeling,named eselect.
> struct eselect_struct{
>     unsigned long readbitmap[MAXBITMAPFD];//suppose the MAXBITMAPFD is 
> MAX OPEN                                         //FD NUMBER PER PROCESS
>     int ret;//-1 on error,non-negative return value is the number of     
>             //acitvity fds
> }
> we can use __set_bit(),__clear_bit(),__find_first_bit()....functions to 
> maintain the bitmap.
> So,you shouldnt scan the fd array any more.

I really don't see why __find_first_bit() is better than "scan the fd array".
They both seem like O(N) operations. You might be dividing the tests by 32 (or
64) but in a busy server with 3000 open sockets, what you really want is no
scanning at all.

Anyway, your problem is already solved. You should check epoll:

http://epoll.hackerdojo.com/

It's been in the kernel for a while, now (with CONFIG_EPOLL=y).

--
Paulo Marques - www.grupopie.com
 
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke (1729 - 1797)