Re: [PATCH] /dev/epoll update ...

[Davide Libenzi]

On 19-Sep-2001 Christopher K. St. John wrote:
> Davide Libenzi wrote:
>> 
>> >     - check new_socket_fd for readable, writable, and
>> >       error. if any true, then add new event to
>> >       event queue, as if the state had changed.
>> 
>> No it does't check. It's not needed for how it works.
>> 
> 
>  Yes, I see that it currently works that way. I'm
> suggesting that it's a needlessly awkward way to work.
> It also results in thousands of spurious syscalls a
> second as servers are forced to double check there
> isn't i/o to be done.

Again :

1)      select()/poll();
2)      recv()/send();

vs :

1)      if (recv()/send() == FAIL)
2)              ioctl(EP_POLL);

When there's no data/tx buffer full these will result in 2 syscalls while
if data is available/tx buffer ok the first method will result in 2 syscalls
while the second will never call the ioctl(). 
It looks very linear to me, with select()/poll() you're asking for a state while
with /dev/epoll you're asking for a state change.

- Davide