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Date: Tue, 12 May 2009 18:59:49 +0200
From: Ed Schouten <ed@80386.nl>
To: Jeff Roberson <jroberson@jroberson.net>
Message-ID: <20090512165949.GF58540@hoeg.nl>
References: <alpine.BSF.2.00.0905111720280.981@desktop>
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Cc: arch@freebsd.org
Subject: Re: lockless file descriptor lookup
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Hello Jeff,

* Jeff Roberson <jroberson@jroberson.net> wrote:
> Once the file descriptor is resolved, we verify the path via the =20
> descriptor table once more to ensure that it has not changed.  At this =
=20
> point, we have a valid reference or we drop an invalid reference and =20
> retry.

It's nice to see someone stepped up to implement this. Just out of
curiosity, have you done any benchmarks to see how many percent of the
time a thread needs more than one attempt to obtain a valid reference on
a common workload?

Maybe it would be nice for diagnostic purposes to add two sysctls to
obtain the amount of successful and unsuccessful attempts.

--=20
 Ed Schouten <ed@80386.nl>
 WWW: http://80386.nl/

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