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.
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