From owner-freebsd-hackers Sat Jun 12 9:55:28 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from dyson.iquest.net. (dyson.iquest.net [198.70.144.127]) by hub.freebsd.org (Postfix) with ESMTP id 3271E15109 for ; Sat, 12 Jun 1999 09:55:25 -0700 (PDT) (envelope-from toor@dyson.iquest.net) Received: (from toor@localhost) by dyson.iquest.net. (8.9.3/8.9.3) id LAA06434; Sat, 12 Jun 1999 11:53:28 -0500 (EST) (envelope-from toor) Message-Id: <199906121653.LAA06434@dyson.iquest.net.> Subject: Re: High syscall overhead? In-Reply-To: <199906121216.OAA13526@freebsd.dk> from Soren Schmidt at "Jun 12, 1999 02:16:21 pm" To: sos@freebsd.dk (Soren Schmidt) Date: Sat, 12 Jun 1999 11:53:27 -0500 (EST) Cc: crb@ChrisBowman.com (Christopher R. Bowman), adsharma@home.com, crossd@cs.rpi.edu, freebsd-hackers@FreeBSD.ORG From: "John S. Dyson" Reply-To: dyson@iquest.net X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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