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. > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > Brian Feldman _ __ ___ ____ ___ ___ ___ green@unixhelp.org _ __ ___ | _ ) __| \ FreeBSD: The Power to Serve! _ __ | _ \._ \ |) | http://www.freebsd.org _ |___)___/___/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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