Date: Sat, 12 Jun 1999 11:53:27 -0500 (EST) From: "John S. Dyson" <dyson@iquest.net> To: sos@freebsd.dk (Soren Schmidt) Cc: crb@ChrisBowman.com (Christopher R. Bowman), adsharma@home.com, crossd@cs.rpi.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: High syscall overhead? Message-ID: <199906121653.LAA06434@dyson.iquest.net.> In-Reply-To: <199906121216.OAA13526@freebsd.dk> from Soren Schmidt at "Jun 12, 1999 02:16:21 pm"
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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. -- 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
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