Date: Fri, 27 Oct 2000 09:42:35 -0700 From: Alfred Perlstein <bright@wintelcom.net> To: Dan Kegel <dank@alumni.caltech.edu> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Jonathan Lemon <jlemon@flugsvamp.com>, Gideon Glass <gid@cisco.com>, Simon Kirby <sim@stormix.com>, chat@FreeBSD.ORG, linux-kernel@vger.kernel.org Subject: Re: kqueue microbenchmark results Message-ID: <20001027094235.C28123@fw.wintelcom.net> In-Reply-To: <39F9AB95.735E26A7@alumni.caltech.edu>; from dank@alumni.caltech.edu on Fri, Oct 27, 2000 at 09:21:41AM -0700 References: <E13oyOE-00044z-00@the-village.bc.nu> <39F9AB95.735E26A7@alumni.caltech.edu>
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* Dan Kegel <dank@alumni.caltech.edu> [001027 09:40] wrote: > Alan Cox wrote: > > > > kqueue currently does this; a close() on an fd will remove any pending > > > > events from the queues that they are on which correspond to that fd. > > > > > > the application of a close event. What can I say, "the fd formerly known > > > as X" is now gone? It would be incorrect to say that "fd X was closed", > > > since X no longer refers to anything, and the application may have reused > > > that fd for another file. > > > > Which is precisely why you need to know where in the chain of events this > > happened. Otherwise if I see > > > > 'read on fd 5' > > 'read on fd 5' > > > > How do I know which read is for which fd in the multithreaded case > > That can't happen, can it? Let's say the following happens: > close(5) > accept() = 5 > call kevent() and rebind fd 5 > The 'close(5)' would remove the old fd 5 events. Therefore, > any fd 5 events you see returned from kevent are for the new fd 5. > > (I suspect it helps that kevent() is both the only way to > bind events and the only way to pick them up; makes it harder > for one thread to sneak a new fd into the event list without > the thread calling kevent() noticing.) Yes, that's how it does and should work. Noticing the close() should be done via thread communication/IPC not stuck into kqueue. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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