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Date:      Thu, 23 Nov 2006 13:29:34 +0100
From:      Ivan Voras <ivoras@fer.hr>
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        freebsd-hackers@FreeBSD.org
Subject:   Re: Kqueue write event position?
Message-ID:  <4565942E.6030004@fer.hr>
In-Reply-To: <20061123121513.U50054@fledge.watson.org>
References:  <ek2ca4$sft$1@sea.gmane.org> <20061123121513.U50054@fledge.watson.org>

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Robert Watson wrote:

> My concern with this idea is that kqueues are not really intended to 
> provide an event stream, rather, notification of a condition.  As writes 
> often come in batches, it's likely that by the time the kevent is 
> received, several writes will have occurred, but only a single event 
> notification will be present.  Is the application you have in mind able 
> to benefit from what is effectively "polled" sampling of writes?  Does 
> it benefit in the presence of writes from concurrent writers, where 
> things like the position and length may depend on which of two or more 
> writers wrote to the file most or least recently?

Yes, this was the next question I wanted to ask. I was counting on 
receiving just the stream of events you describe - receiving random 
samples of it would be as useful as only receiving write notifications.

Thanks for clarifying this!



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