Messages in this thread | | | Date | Wed, 30 Oct 2002 21:04:31 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: and nicer too - Re: [PATCH] epoll more scalable than poll |
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On Wed, 30 Oct 2002, Martin Waitz wrote:
> On Tue, Oct 29, 2002 at 06:24:27PM -0800, Davide Libenzi wrote: > > You have two ways to know if "something" changed. You call everyone each > > time and you ask him if his changed, or you call everyone one time by > > saying "call me when you're changed". > well, you don't say 'call me when you're changed' but > 'i'm interested in your status, please be prepared to report if you > have changed' when calling epoll_ctl.
Yes, I just don't like to write much :)
> > It's behind the "call me when you're changed" phrase that lays the > > concept of edge triggered APIs. > in most situations, you are not really interested in 'has it changed?' > but in 'what has it changed to?'. > this is the difference between edge- or level-triggered notification. > > e.g. the application wants to know > 'from which fds can i read without blocking' and not which fds > happend to change their block-state > (perhaps there is still data available after the last read, in > which case the application would like to be notified about this > situation)
The state of I/O can change only in two way. From I/O space available ( 1 ) to I/O space empty ( 0 ) and reverse. You generate 1->0 transactions and I guess that ones are not very interesting. You're very much interested in 0->1 transaction indeed, that the kernel generates.
> is it possible that www.xmailserver.org is down atm? > i couldn't get as much docu about epoll as i wanted to, > so please correct me if my above view about epoll is incorrect > > and yes, i haven't looked at any code yet, > i just like the kevent docu better then the epoll docu... ;) > and yes, i would like to port kevent to linux, > but i don't have any time to do this in the next months... :(
It has always been up for what it may concern. It's a T1 but during these days it had quite a few hits because of epoll.
- Davide
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