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SubjectRe: > 15,000 Simultaneous Connections
On Tue, 7 Sep 1999, Rogier Wolff wrote:
> I would then prefer to go with the API that the digital guys suggested
> in: http://www.cs.rice.edu/~gaurav/papers/usenix99.ps
>
> #define EVENT_READ 0x01
> #define EVENT_WRITE 0x02
> #define EVENT_EXCEPT 0x03
>
> typedef struct {
> int fd;
> unsigned mask;
> } event_descr_t;
>
> int declare_interest (int fd, int interestmask, int *statemask);
> int get_next_event (int array_max, event_descr_t *ev_array, struct timeval *timeout);
>
> If you want, you can then simulate select in the library.
>
> int select(int n, fd_set *readfds, fd_set *writefds,
> fd_set *exceptfds, struct timeval *timeout)
> {
>
> It should just pass on the call to the system call for small nmax.
>
> if (n < 256)
> return sys_select (n, readfds, writefds, exceptfds, timeout);
>
> When nmax goes above a certain threshold, it will become viable to
> compare an old cached version of the arrays to the current one,
> register the differences with declare_interest, and then empty the
> event queue. (For the example, I'll work bit_wise, but the actual
> implementation will work with a long at a time.)

as much as i like gaurav's model, there are still some interesting issues
to be worked out.

there doesn't appear to be a way to create more than one event queue per
process. for instance, you *can* emulate select() in the C library with
the new API, but what if the application also wants to use the new API?
what happens when the select() emulator picks up an event that was
destined for a different event handler? can it push the event back onto
the event queue?

- Chuck Lever
--
corporate: <chuckl@netscape.com>
personal: <chucklever@netscape.net> or <cel@monkey.org>

The Linux Scalability project:
http://www.citi.umich.edu/projects/linux-scalability/


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