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From: Chris Friesen <cfriesen@nortelnetworks.com>
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To: Mark Mielke <mark@mark.mielke.cc>
Cc: John Myers <jgmyers@netscape.com>, Dan Kegel <dank@kegel.com>,
       Davide Libenzi <davidel@xmailserver.org>,
       Benjamin LaHaise <bcrl@redhat.com>,
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       linux-kernel <linux-kernel@vger.kernel.org>,
       linux-aio <linux-aio@kvack.org>, Andrew Morton <akpm@digeo.com>,
       David Miller <davem@redhat.com>,
       Linus Torvalds <torvalds@transmeta.com>,
       Stephen Tweedie <sct@redhat.com>
Subject: Re: epoll (was Re: [PATCH] async poll for 2.5)
References: <Pine.LNX.4.44.0210151403370.1554-100000@blue1.dev.mcafeelabs.com> <3DAC9035.2010208@netscape.com> <3DADC5F8.60708@kegel.com> <3DAEF6DC.9000708@netscape.com> <20021018170024.GA13087@mark.mielke.cc>
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Mark Mielke wrote:
>>>>>   while (read() == EAGAIN)
>>>>>       wait(POLLIN);
>>>>>
> 
> I find myself still not understanding this thread. Lots of examples of
> code that should or should not be used, but I would always choose:
> 
>    ... ensure file descriptor is blocking ...
>    for (;;) {
>        int nread = read(...);
>        ...
>    }
> 
> Over the above, or any derivative of the above.

The main point here is determining which of many open connections need servicing.

select() and poll() do not scale well, so this is where stuff like /dev/epoll comes in--to tell you 
which of those file descriptors need to be serviced.

Chris



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