Date: Sat, 12 Jun 1999 14:14:09 -0400 (EDT) From: Brian Feldman <green@unixhelp.org> To: "John S. Dyson" <dyson@iquest.net> Cc: Soren Schmidt <sos@freebsd.dk>, "Christopher R. Bowman" <crb@ChrisBowman.com>, adsharma@home.com, crossd@cs.rpi.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: High syscall overhead? Message-ID: <Pine.BSF.4.10.9906121412490.8587-100000@janus.syracuse.net> In-Reply-To: <199906121653.LAA06434@dyson.iquest.net.>
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On Sat, 12 Jun 1999, John S. Dyson wrote:
> Soren Schmidt said:
> [Charset ISO-8859-1 unsupported, filtering to ASCII...]
> > It seems Christopher R. Bowman wrote:
> > [exelent explanation snipped]
> > > The alternative to the Giant Kernel Lock(tm) is so called fine grained locking
> > > wherein locking is pushed down closer to the data structures. In fine grained
> > > locking two processors might be executing in the kernel at the same time, but
> > > only if they didn't need the same resources. On might be doing a disk read
> > > while the other queues up a character for the serial port. The fine grained
> > > lock has the potential for higher parallelism and thus better throughput since
> > > process may not have to wait as long, but the larger number of locks with their
> > > many required lock and unlock operations add overhead and further the design is
> > > more difficult and error prone since the interaction of the numerous locks may
> > > result in deadlock or livelock situations every bit as problematical as the
> > > problem they try to solve.
> >
> > There are also those of us that dont belive in finegrained locking, exactly
> > because of all the small locks you have to check/lock/open, the overhead is
> > not worth it.
> >
> Finegrained locking either requires developers with IQ's of 200 or higher,
> or a different kernel structure. I suggest that finegrained locking is cool,
> and can be intelligently used to mitigate (but not solve) the effects of
> lots of problems -- however, it would be unwise to embark on an effort to make
> the FreeBSD kernel into an efficent 16way SMP kernel by using finegrained
> locking all over the place.
But your microkernel-hybrid BSD will do 16way SMP with a fully-parallelized
kernel?
>
> --
> John | Never try to teach a pig to sing,
> dyson@iquest.net | it makes one look stupid
> jdyson@nc.com | and it irritates the pig.
>
>
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